Another European war!?!
So are Australia, China, Japan, Indonesia, India, Russia, Africa all considered European now? Like it or not the Nazis would have taken over the world if they had not been stopped, and no you would not have stopped them if you'd stayed neutral because you would have then stood alone against a country spanning the rest of the globe. Their resources would have simply been to great to compete with.
As for casualties, yes, they were horrific, but the US suffered nothing like the others. Britain suffered twice what the US suffered and the Russians suffered even more with over three million military casualties. Try to remember that millions gave their lives so you could HAVE and opinion and not have to speak German in a slave camp.
WW2 Casualty list