The bigger issue has been that illegal immigrants count for the purposes of Census and therefore contribute to states with a lot of illegal immigrants getting more representatives in Congress.

Well, the U.S. Constitution requires that the Census determines the number of people, not the number of citizens. Trump tried to change that during his first term and SCOTUS smacked him down.

Been there, done that.

… the question whether noncitizens should be excluded from the apportionment base was discussed at length during the debates over the Fourteenth Amendment. During those debates, many members of Congress urged that only citizens or voters should be counted in determining congressional representation, insisting that foreigners who had arrived in America should not count for purposes of apportioning representatives to Congress. Following more than seven months of heated debate in Congress, the Fourteenth Amendment reaffirmed the federal government’s duty to count the nation’s whole population, including the entire immigration population, in apportioning representatives to Congress.
A count of the total population, Sen. Jacob Howard explained, is “the safest and most secure principle upon which the Government can rest. Numbers, not voters; numbers, not property; this is the theory of the Constitution.” The authors of the Fourteenth Amendment refused to “strike from the basis of representation the entire immigrant population not naturalized,” insisting that “[u]nder the Constitution as it now is and as it always has been, the entire immigrant population of this country is included in the basis of representation.”