As a fan of rail, although not a railfan, I am acutely aware of a variety of these projects, and the sad reality is that they are currently unlikely to move forward for a variety of reasons, but the most important are:
- Competition from freight
- Competition from airlines
- Distance between cities
- Low cost of fuel
Competition from Freight
Although U.S. passenger travel is relatively poor, the freight lines are excellent. U.S. rolling stock is on average much larger than rolling stock in Europe and in Asia because it is focused on freight. Per pound shipping by train for raw materials (e.g. coal, gravel) and larger products (e.g. cars) is much more efficient by rail, and is critical to this day for economic production in many cities not on a coast, like St. Louis, Dallas or Chicago.
When the U.S. created Amtrak to take over passenger rail, in most instances freight lines retained the rail. Not only that, but the lines often have the right of way as well, so even if other lines were to be built the freight lines would have priority. The trade-off for most freight is speed for cost, which is a trade off passengers are unwilling to make, but the freight lines have many legal rights, and are the source of a lot of know-how about running a line.
Competition with airlines
Airlines compete in two ways: blocking construction and undercutting prices. Texas is as close to an ideal location to build new high-speed rail as is possible: low land costs, few legal and political impediments, and even a private intiative to build a high speed rail and yet there isn't one yet. Part of the reason is opposition from Southwest, one of the major discount airlines which has a core business doing flights around the four big Texas cities. Of course, now that Southwest has a more global focus, its opposition is lower, but it was enough to stop progress for decades.
Even without direct political opposition, there are few situations where rail travel would be quickly competitive with air travel immediately. The bread and butter of all passenger service is business travel, and they are already used to air travel, so you would have to convince them quickly. Business people need point to point travel rapidly, since time is money. Attempting to bridge the gap with tourist travel will actually alienate business travelers, turning commercial ventures into what Amtrak is now--a slow moving land cruise--which tourists don't mind, but business-people would hate. If you could reduce security concerns, rail could make up the difference some with reduced time at the station, but most frequent travelers (i.e. the people who make up the lion's share of profit for airlines) are already minimizing that time with programs like Pre-Check, so there isn't as much gain to be made there.
The bottom line is that until rail is cheaper than flight, it will consistently lose out on business traffic, and tourism. It will never be faster, except in a few mid-level distances.
When rail was first introduced it was a godsend for U.S. cities which are ages apart. As long as the competition was horseback or carriage, train won hands down. Once air travel became available, however, those distances worked against it. Flight is just so much faster than rail.
High-speed rail mitigates that at distances of about 200-300 miles. Those distances are fairly common in Europe, but rare in the U.S. Los Angeles and San Diego, which are often thought of as being in the same Megalopolis are actually over 100 miles apart, which is another country for many places in Europe. They may be the closest two cities, other than the Eastern seaboard, or twin cities like Minneapolis-St. Paul, or Dallas Ft. Worth, which themselves are nearly 100 miles apart.
Even in close cities, the geography of the city works against rail. It is frequently only economical for those relatively near a train station to travel by rail. This is not a problem in really old cities, where populations are concentrated near a center. In the U.S., even cities like Chicago and St. Louis are very spread out, leaving the option of having a single station at either end of the route, where the customer base will only be the relatively low population center, or multiple stops to make it attractive to more locations, but increasing the time making it less attractive to certain kinds of passengers.
This is the problem with the currently proposed rail between Chicago and St. Louis, until there are hourly or more frequent trips it will be inconvenient for anyone outside the Chicago or St. Louis city area to take the train (i.e. most of the people who might want to use it). Even someone who lives in Aurora could drive the majority of the way between Aurora and St. Louis in about the same time it would take to drive to Chicago, board the train, take the faster-than-driving-train to St. Louis, and that isn't accounting for waiting for a train! If you start adding stops at places like Aurora, Springfield, etc. then the trip becomes shorter for them but longer for the people who are near Union Station, making that a less attractive option there.
In the end, all of this goes away if fuel becomes too expensive. Whether car or air travel, the reason that it is affordable to travel those ways rather than train is that the fuel is not too expensive. Unfortunately, fuel would have to be somewhere near $10 a gallon or more before rail becomes an attractive for most people. It is conceivable that the government could tax fuel that much, and the $10 a gallon figure is thrown around in political circles on the left precisely for this reason. However, if that were true then all of the supply chains that currently rely upon trucks would have to be reconfigured--and every supply chain would still have trucks.
Transition costs would eat up any advantage for several years and inflict egregious damage on the economy. In the long run it might work out, but it might not. There distances between cities would still exist for example, and you could end up with no good airlines and no reliable train travel.