Sorry - I just have to stick my two cents in...
In such a scenario, i would predict that the UK and not the US would be the victor in such a scenario. Why?
1. We dont have the home town advantage.
2. The brits have a tendency to get alwful mad when someone attempts to invade them...all of them.
3. Ever tried to land navigate across the british country side?
4. I dont think the rest of the european nations would give us a place to jump off at to invade UK. that means starting everything from US...and dragging it to UK.
5. What have they got that we'd want anyway...a better serving of fish and chips?
Seriously...despite the US might there will always be an England