Don’t Force Us To Be A Part Of It
It would appear that the United States of America has been called upon to provide assistance to the United Kingdom on a number of occasions ever since the United States of America made the decision to chart its own path (by which we mean, ever since the American Revolutionary War in 1776).
In Harry Potter, we can’t help but ask why they didn’t volunteer their assistance during the battle against Voldemort. We presumed that they were only biding their time until they could return to their English colleges in the Old World and let Voldemort have his way with it there.