The United States has, at best, 51 different voting systems in a federal election. There is no centralization by design. That's 51 different voter registration

The United States has, at best, 51 different voting systems in a federal election. There is no centralization by design. That's 51 different voter registration laws, 51 different sets of candidates, 51 different ballots, 51 different voting procedures, etc. Each state's laws have been subtly (and sometimes not so subtly) changed to provide a benefit to whoever was in power at that time.