In the year 2020, how hard is it to have a national voter database? Hey...when you die, and your death certificate is issued, your voting record is disabled! Hey...when you show up to vote in Florida on election day, and it says you are registered in Georgia - you F’ed up. But to give you the benefit of a doubt you are issued a special ballot that may or may not be counted, depending on how the difference between the winner and the loser. If the election is too close to call, you come and prove you are a resident. You don’t - and its tossed. Vote in Florida and then try to go vote in Georgia - it says you already voted today.
Without the political will, impossible. We don't even know how many illegal aliens are in the country.