Good point.
I’ve heard that some estimates, are that California would lose at least 3 House seats, if illegals weren’t counted in previous censuses.
The same could be true of some other immigrant heavy states such as New York.
Since the purpose of the census is determining Congressional representation, and since illegals or legal resident aliens are not allowed to vote, the numbers of non citizens should not be involved in determining Congressional representation.
A unanimous Supreme Court ruled Monday that illegal immigrants and other noncitizens can be counted when states draw their legislative districts, shooting down a challenge by Texas residents who said their own voting power was being diluted.
https://www.washingtontimes.com/news/2016/apr/4/supreme-court-illegals-count-apportionment/
2010 census counted
Foreign Citizens In The U.S.
Citizens of foreign countries living in the U.S. - Counted at the U.S. residence where they live and sleep most of the time.
Citizens of foreign countries living in the U.S. who are members of the diplomatic community - Counted at the embassy, consulate, United Nations’ facility, or other residences where diplomats live.
Citizens of foreign countries visiting the U.S., such as on a vacation or business trip - Not counted in the census.
Supreme Court was unanimous in counting illegals.
A unanimous Supreme Court ruled Monday that illegal immigrants and other noncitizens can be counted when states draw their legislative districts, shooting down a challenge by Texas residents who said their own voting power was being diluted.