I don't think it is a crime to register a non citizen, but it is a crime for that person to vote. They are given ample notice of their ineligibility and the "they let me do it" argument doesn't excuse them.
“””I don’t think it is a crime to register a non citizen, but it is a crime for that person to vote.”””
In Florida it is a 3rd degree felony for a non-citizen to register to vote.
You may want to check the law in your state, but I suspect your state’s laws also impose a felony for non-citizens registering to vote.
The fact that millions of non-citizens may have registered to vote is enough to convict them of a felony and immediately deport them.