The Census Doesn't Work Like That
"The census" - as in the official decennial United States census is not based on a sample. The Census Bureau will attempt to collect information from every household in America.
You can read about this in their 2020 Operational Plan (pgs 8-9). They send forms to every household in the United States. People may complete their census form either online or on paper. Households which do not return a census form will be contacted in person by a field agent, who will attempt to survey them in person.
This is all just to say that although the decennial census is a survey, it is also a direct measurement of the population. It is not a sample-based design like many other surveys are. Therefore, there is no sampling error.
That being said, realistically not everyone will respond. In 2010 about 74% of households participated in the census (2010 Census - Take 10 Assessment Report, pg10). Although the Census Bureau has a Nonresponse Unit which attempts to drive up that number, they also use imputation deal with missing data.
The operational plan and CCM workshop documents both include imputation as a possible approach. For example (from the operational plan) says that the Response Processing unit (which deals with data that has been collected) may:
Create models based on established business
rules to determine the appropriate course of
enumeration action for cases (e.g., person
visit, use of administrative records and third-
party data, or imputation)
Imputation is a process for "filling in" missing data. Since imputation (and the rest of the work done by the Response Processing unit) is done prior to publication, all these corrections will have been made prior to the data being published.