This is quiet a false dichotomy you're running with here. You write as if the only choice is between funding global military efforts at their current levels or caving to the Nazis.
Of course declaring war on Germany upon their invasion of Poland was the right thing to do. But it doesn't make declaring war before that the even righter thing to do. And it has little bearing on our choices today, that was another time. You can't use Hitler to justify WWI or the Crimean war or the Punic Wars. What makes him a better justification for building the war machines in Iraq or Aghanistan?
There are many choices. We could spend the same money we do now on the military but only focus on defensive weapons. We could educe our spending on military by half and still be funding our military far above the level of most other countries. We could significantly draw down our military as we did after nearly every war in our history. Those are all choices. But we choose to spend incredible sums on forces which can project power around the entire world. We do that for a reason. It isn't entirely sinister but it isn't entirely altruistic either. In the end, we do it because it gives us power. For the exact reason the Athenians grew their "alliance" sometimes at the point of a sword. It gave them power.
Putting that all aside, the best case you make for war is that it might reduce suffering and prevent tyranny. Well that is precisely the best case for publicly funded scientific, medical, safety and poverty efforts. Which is exactly the OP's point.