The American military did not "invade" the UK (please learn the difference between the UK and England). They were allies in the same war. Britain saved the USA just as much as the USA saved Britain. It is not that I don't appreciate the contribution the USA made in WWII - but I object to the idea that the USA did so as a sort of charitable contribution to give a helping hand, or that the UK was barely hanging on until the USA stepped in to show us how to fight a war properly.
If the USA had not entered the war in Europe, the UK and USSR would probably still have won - but it would have taken a lot longer, and cost much more. And the USA's immediate enemy, the USSR, would have been much stronger afterwards. Had things turned out differently and Germany had beaten the UK, then after they had consolidated their power over Europe they would have proceeded to dominate the USA (economically and then culturally - they may not have had to invade). Again, this would have taken time - but it was a very real risk.
The USA did the right thing by joining the UK in WWII - but they did it because it was the right thing for the future of the USA, not because it was helping the UK. (Again, I do not blame the American leadership for putting themselves first - that is the prime responsibility of any government.)
Fair enough.
It's a pity democracy works so badly in the USA - how you manage to regularly elect leaders whom you dislike and distrust so much is beyond my comprehension. In Europe, there is usually a solid proportion that dislikes any given prime minister, but we not to the extent that seems to happen in the USA, and most of us have a good deal more confidence and trust in their governments. Maybe European leaders don't try to do as much or change as much, and thus there is less fear of their mistakes?