Why has no-one mentioned this?
First of all, I haven't seen the other 'Puppet Master' films, so I wasn't aware right away that the boy was meant to be American. I assumed (naturally) that as the film started in 1939 and he was talking about troops going to fight the Germans, that he was Canadian. But no, apparently the USA entered the war against the Germans and the Japanese in 1939!
Does this come from some comic book fantasy series that assumes 'what if the Americans and Japanese were in the war from the beginning'? This is a genuine question because apart from that I quite enjoyed it 9apart from the very obvious flaws). If it's NOT 'what-if', I won't bother trying to watch the others.