In the 1920s a state fresh off a recent regime change disappearing would have been extremely par for the course. You telling that to someone from the 1960s would probably have more of an effect.
I mean, if you showed them a map it'd look nothing like their current political divide. I'm not sure they'd be more shocked by the state of what then was Soviet Russia than by Czechoslovakia being broken up or the other half a dozen changes in Europe alone.