Germany is less surprising to me, given the history involved. Based on what I am looking into on Google Maps, however, it hardly seems to be a phenomenon confined to the US, and at least based on my spot checks it seems to be more common than not for public schools to display national flags.
You really think that the USSR of the early 1940s could have fought that era's Germany and Japan at once?
What about the comments by no less than Admiral Zhukov himself acknowledging that in his view, the USSR couldn't have defeated Germany without US assistance?