If America decided to wipe Italy off the map, you would be happy for the UK to send some money? That would be enough?
I don't think you can impose enough diplomatic sanctions on America to make us care, and certainly not enough to make up for deleting Italy.
If you would be sanctioned into oblivion like North Korea, you would probably care at some point.
Attacking one of the world largest Western economies, would turn the other ones against you