France and Germany are together in all their EU Alliance goodness. America finds himself more jealous then feels he should be over this (he's had crushes on the both of them for as long as he can remember even when he shouldn't) and it doesn't help matters that everyone else in his life is all paired up and happy while he's left all on his own. Sensing something is wrong France eventually pries the truth from him. Then of course he asks America if he'd like to join them. America acts appalled at the suggestions and declines until a few sleepless nights thinking about it drives him to appear on their doorstep one evening.

Threesome antics of your choice happen from there any pairing order is fine though I do have a thing for America-based sandwiches. ;-)