England was once America's big brother/daddy figure before the American Revolution. They're friends again but they haven't really had a heart to heart about their past. Or you can read my silly app for the story in detail. Generally character relations in Hetalia have a faint resemblance to the actual real countries though there's wiggle room and fans have ships and headcanons an such, etc.

Since they're both idealists they'll probably get along naturally. ^^