Saik0

Citizenship is already required to vote in state […] elections.

This is incorrect. The law you think you’re referencing by this is only applicable to Federal positions. Several states explicitly allow non-citizen voting in local elections. Many have no laws on the books at all addressing it. Only 15 states explicitly prohibit non-citizen voting for local positions.

https://ballotpedia.org/Laws_permitting_noncitizens_to_vote_in_the_United_States

This fact alone should mandate that the federal level maintains their own registrations. The State and Federal levels have different applicable voter rolls because the state doesn’t have the same requirements as the federal elections.

Edit: Wrong word.