Having just stepped into the shoes of Ronald Reagan on Season 2 of “Fargo,” Bruce Campbell once again demonstrated his unique ability to deliver an uncanny impression. Donning glasses, Campbell looked eerily like the new “Late Show” host and his brief stint behind Colbert’s desk did not disappoint. The “Evil Dead” star’s impression lasted merely one word, “Nation,” but between the pencil tapping and desk banging, it was clear that Campbell did his research.