In the US, at the level of the various branches such as the White
House, DOE, NASA, Supreme Court, Circuit Courts, etc., there are such
comprehensive newsrooms, as far as I can tell, but I've not been able
to find equivalents for the overall Federal government nor for all the
state governments, D.C., Puerto Rico, etc...
Are there such equivalents in the US?
There is not a comprehensive source of official statements at either the federal level, or (at least in every U.S. state of which I am aware) at the state level.
The accepted practice is for individual agencies or components of a decentralized governmental structure to have separate public relations officers and online sources of information.
Even within a single county or municipal government, it is the exception rather than the rule for there to be a single coordinated source of messages to the general public from that governmental entity.
Basically, new gets out faster when needed when different agencies can directly release their messages to the public, and decentralizing the news distribution avoids the risk that senior people in the administration are held responsible for having government messages attributed to them without their consent.
For example, many law enforcement agencies have twitter accounts over which they provide regular news releases, and those accounts are not coordinated with their parent agency or other law enforcement agencies in any meaningful way on a day to day basis and are not aggregated with each other in any official forum. See, e.g., the Denver Police Department twitter account.
Similarly, the National Weather Service has a comprehensive system for issuing weather reports to the public, which is partially coordinated with emergency management systems, but this federal agency does not consult with the White House before issuing these reports and these reports are not aggregated by an official source with other federal government press releases.
Back Channels and Leaks
In addition, many government officials and agencies utilized unofficial back channels to share information with the public, usually through a media source, with off the record statements that are not formally attributed and leaks of information that is confidential or classified.
In the Pentagon Papers case in 1971 decided by the U.S. Supreme Court basically immunized the private media parties to these back channel communications from liability for receiving information through these channels, although the leaking parties are still exposed to legal liability, and many states have recognized a legal privilege for reporters permitting them to refrain from disclosing their sources to courts and other authorities in these situations.
The government officials engaged in this conduct, however, unless secretly sanctioned by someone with the authority to release the information, do so at risk of personal criminal liability (as happened, for example, in the case of CIA leaker Joshua Schulte on July 13, 2022) and at risk of being fired from what is otherwise secure civil service employment.
Private News Aggregation
In the U.S., instead, the task of monitoring the fire hose of government news releases from myriad different sources and making sense of them fall to private media outlets (including commercial and non-profit news organizations, search engines, news aggregator services (e.g. RSS feeds), non-profits arrangements like the Stake Exchange network, social media platforms, and private individuals).
In addition to media platforms directed at the general public, almost every industry and professional or non-professional specialty has a network of specialty new outlets (sometimes called the "trade press"), journals, blogs, wikis, limited access social media forums, and associations to coordinate the flow of information from government and other sources to people interested in this information.
Efforts To Coordinate Communications To The Public
Sometimes multiple different agencies coordinate to provide a common message, and the President or a Governor, respectively, can impose some message discipline (although not completely as some subdivisions of the federal government and some subdivisions of the state government are independent of the President or Governor respectively). But, these are the rare exceptions to the general rule, rather than the norm as it would be in the case a most private business corporations.
For example, the federal Emergency Alert System, usually used for natural disaster alerts or similar calamities, works in this way.
One notable example of such an effort to impose message discipline in the U.S. federal government arose in the early days of the Trump Administration when the White House established standards about what U.S. federal agencies could and could not communicate to the public, suppressing, for example, a great deal of previously publicly available information related to climate change, banning certain "buzz words" that were felt to reflect a liberal world view, and requiring more centralized approval from the White House Office to release certain kinds of information. See, e.g., this January 24, 2017 report from the Washington Post entitled "Federal agencies ordered to restrict their communications." Over time, however, these efforts at maintaining message discipline from federal agencies by the White House were relaxed somewhat with little fanfare or official recognition. While Presidents have the authority to do this, to a great extent, however, most Presidents have found it unwieldy and not worth the trouble to attempt to do so.
Another example of efforts to impose message discipline upon what state officials in one part of government say, enacted legislatively rather than by executive branch action, is the "Don't Say Gay" bill recently enacted in Florida limiting what public school officials can say with regard to LGBT+ matters. A statute was necessary to achieve this because in Florida, as in most states, primary authority over K-12 public schools is vested in local elected school boards, which a separate special district local governments that do not report directly to the state department of education (which reports to the Governor). The state department of education, instead, as is common in U.S. state and local government, has only limited administrative supervisory authority of local school board operations.
Notable Federal Public Communications Institutions
The only area of news releases that is centralized at the federal level, and which often, but not always, has a parallel state arrangement, is the Federal Register, which is the mandatory forum in which the public is given notice of new proposed or adopted federal regulations, as a result of the Administrative Procedures Act of the federal government. This is not mostly directed at the mass media, however.
The U.S. has an institution known as National Public Radio with a parallel public television network, but these are independent non-profit entities (more independent than, for example, the British Broadcasting Corporation upon which it was modeled) that have programming that includes but is not limited to news programming, that is funded in part by independent federal agency grants, and in part, from other sources like listener donations and corporate sponsorships. NPR is meant to be an independent private media entity that covers the news that happens to have government funding, rather than an official instrument of government communications to the public.
The U.S. also has an institution known as the Voice of America, over which the U.S. State Department has far more editorial control despite affording it some independence, which is a radio network intended to provide U.S. endorsed or supported news reporting to foreign listeners that while seeking to be credible and accurate as a news source, is ultimately a propaganda engine. But, this too is not a comprehensive or official source of all federal government press releases.
Something of the inverse kind of coordination does occur in the U.S., which is that all publicly held company filings with the Securities and Exchange Commission of the U.S. federal government, which include almost all significant news releases of big businesses, have to be posted to the SEC's EDGAR system, although this is not always the first place that this new becomes available, so time sensitive securities traders need to gather news from many other, more timely sources, such as publicly held company conference calls which are held periodically with interested securities professionals, financial journalists and investors.
Similarly, a variety of other public records, from private persons and government agencies alike, are made available to the public in real time or close to it, such as aircraft ownership and lien records, intellectual property ownership records, and certain kinds of federal court records (which are made available to the public in real time via the federal court's PACER system).
Why Is The U.S. Different From Canada In This Regard?
One of the reasons that Ontario is more coordinated than the U.S. federal government, or U.S. state governments in this regard, is that Ontario's government is organized in a Westminster style parliamentary system in which all parts of the legislative and executive branch are basically fused in a cabinet led by a first minister in which one of the core foundational rules of this parliamentary system is that: "All ministers, whether senior and in the Cabinet, or junior ministers, must support the policy of the government publicly regardless of any private reservations." This hard wires concerns about centralized message discipline right into the core of the political model. In such a model, having a centralized public relations officer for everyone who reports to the cabinet makes perfect sense.
In contrast, in the U.S., the federal government has a stark separation of powers between the executive, legislative and judicial branches, and between subcomponents within it, there are many agencies and officials who are wholly or partially independent of the President, and there is no Westminster style parliamentary system custom of suppressing external expressions of dissent.
State and local governments in the U.S. are even more fractured, with state constitutions often establishing plural executive branches with some functions handled by elected officials independent of the governor or other top local government governing body, in addition to the divisions present in the federal government.
Another historical reason for the aversion of the U.S. political culture to having a coordinated source of public news releases is that this kind of coordination was associated with the late 19th century and early 20th century political machine politics, in which a political party that controlled a governmental entity would coordinate all activities of governmental entity through backdoor party institutions rather than formal governmental institutions, in a political culture that was widely associated with corruption, which the progressive movement and good government reformers sought to disrupt. Centralizing communications to the public "smells" too much like political machine politics to many participants in the U.S. political system.