Close votes generally trigger recounts. As far as the mail-in ballot, well, there are states that do virtually all of their ballots by mail -- and their citizens are happy with that. Early voting used not to be a thing; now nearly every state has early voting. Each state does their own thing as far as voting is concerned (including voter suppression, now effectively without the Voting Rights Act to mess with them), and as a country that's how it's been done since the beginning.
Now all of a sudden all these states-rights folks, who scream bloody murder if you mess with some state's right to have whatever law about abortion or gun control, are screaming bloody murder for the federal government to effectively take over (i.e. validate and/or recount) elections. Because they trust that a Trump Administration-selected group will come to the "right" answer, because, after all, it's inconceivable that their little bubble-generated certainty that Trump would be re-elected in a landslide is actually wrong.
Wendy P.