I think a possible reason why Centaurman has time stopping powers might be because the centaur Chiron, the trainer of such heroes as Hercules, Jason, and Perseus, was the son of Chronos, the Titan God of time. But of course that's just my personal theory.
It's pretty dang obvious that Yamatoman is weak to Tomahawkman's weapon because the US was the first and only country to truly defeat Japan in war and occupy it. _USA! USA! USA! USA!!!_ And in that case, if Plantman maybe actually represented Southeast Asia afterall, then that represents how Vietnam defeated the US in, that's right, the 1980 World Softball Cup when Vietnam beat the United States 7 to 4. _(Just kidding, Vietnam never defeated America in anything ever. 😂)_
I sure do like the idea of national Robot Masters. Knight Man and Blizzard Man are my favorites. Knight Man because of his design and Blizzard Man because he HAILS pun intended from Canada.