> Don't believe he had anything to do with Czechs
Most Slovaks, Rusyns, Hungarians who lived in Czecho-Slovakia before WW II didn't. The Slovaks called themselves Slovaks, etc., but their citizenship as formally seen by the U.S. had nothing to do with their own identity.
The answer addressed only what the U.S. government saw them as during WW II: the State Department saw them as citizens of (the then non-existent) Czechoslovakia. Those are the wonders of international diplomacy. That's all.