It is of course only quite resonantly that Muggles have gained enough firepower to be a threat to shielded wizards.

It is mentioned that Grindelwald confunded Neville Chamberlain, and that the Nazis were his "muggle pawns". So I think its probable that "Imperious a few heads of state" has already happened and the result was WWII.

McGonagall would probably want to use a different method that didn't involve unforgivable curses though.