Czechoslovakia was one of very very few (two, to be exact) countries that factually had Western guarantees, AND it was in a position to really contribute should the West have decided to stop Hitler early on - but the future Allies preferred to go Munich instead. So, yes, I personally do have a problem with UK and France jolly jumping into wars over Estonia or Bolivia.
USA guarantee the independence of Bolivia at games opening, as they did in real life.
You seem to be stuck between saying the games not realistic for adding guarantees whilst advocating a minor expanding to world dominance in the space of 10 years, in which case ask yourself what is more problematic? I can't imagine how you'd have felt on HoI 3 where it was really difficult for minors to aggressively expand as it was in real life!