Yeah, Hitler explicitly referenced US imperialism I believe, when he talked about "Lebensraum" in the East. He had a similar racist rationale, why it would be ok to subjugate the slavs. This is not what I meant though. If Europeans as a whole came to realise the tremendous opportunity that a shared European continent means in terms of shared wealth and prosperity, I don't think anyone in their right mind would want to revert to nationalism, especially when they are from tiny countries like Belgium or the Netherlands. I also believe this is how most young Europeans think, judging by my encounters with Greek, Italian and Spanish students in Germany.

There is no need to conquer anyone, if it is mutually beneficial to cooperate and compete with external forces instead, such as the US and China.