England and America have adopted a kid, a little girl, and they are perfectly loving parents. America is just more slightly overprotective of his daughter than you would have expected, not just of her safety but also her happiness so much so that he scares the other nations and many humans with his threats (which everyone knows he can and will follow through on) but then goes back to being sweet and loving with his daughter (who is young, about eight).

Bonus: England watches and approves, following up with more subtle threats if America's don't work.
Bonus 2: The first ones to annoy America are the Bad Touch trio.

General mood of Eminem's 'Mockingbird' here - if the mockingbird don't sing and the ring don't shine/ I'mma break that birdie's neck/ I'll go back to the jeweller who sold it to ya and he'd gimme every carat don't fuck with dad