You should brush up on your history. First World War had nothing to do with "white supremacy" - every side whose opposition led to it was lily white, Germans, French, Belgians, Russians, British, Sebrians, whoever you point to - they where white. It was a very complex tangle of reasons that led to the war, but "white supremacy" had zero to do with it.
Second Word War, as we all know, has been mostly led by Nazis, who were, among other things, undoubtedly very very racist. However, even then they gladly paired with Japanese - most definitely not "white", Arabs - not really considered "white" by most Nazis - to achieve their goals. And they had absolutely no problem suppressing and massacring Eastern Europeans (very "white") when it suited them. Their goal was, ultimately, world domination under the aegis of the Nazi party, and their "white supremacy" was mostly "Nazi supremacy" - if you were white but not agreeing with Nazis, you were dead. So it was a standard totalitarian approach, which is no different in any totalitarian regime, racism notwithstanding. Nazis where definitely racial supremacists (though just "white" didn't go nearly far enough for them) but even if they weren't, it would end up in the same way.
And as history teaches us, totalitarian regimes like to expand, if they can, and cause wars, if they have resources for it (fortunately, North Korea has none, but even then they are trying to provoke something constantly).
> A white nationalist uprising in Europe would be deadlier
There is no white nationalist movement in Europe even close to pulling something like this off. In fact, I don't think there's even one serious "white" nationalist movement in Europe at all - most nationalist parties are specifically "nationally" nationalists - e.g. French nationalists, British nationalists, Hungarian nationalists, etc. and they couldn't care less about other "whites" as soon as they aren't French, British or Hungarian. Of course, racial movements exist too, but again - they are minuscule compared to nation-based movements.
OTOH, ISIS has already pulled off a major war in Middle East, and while it fortunately looks like they're ending up on the losing side now, it already cost major loss in life and economic damage, and it is very far from the end. Taliban in Afghanistan is far from being beaten too. They are massively in force right now, while "white nationalist uprising" is nothing but an extremely unlikely hypothetical.