Ok can you help me settle a debate with my mother? Here is the story - my mom was born in the US in '43, after her mother emigrated from what my grandmother always called Austria. But here's the catch - when my mom was 8ish (call it 1950) they went back to my grandmother's "Austrian" hometown, where my mother has vivid memories of having to hide from the RUSSIAN troops in town. I'm figuring that this means my mother was actually in Hungary? And perhaps this confusion is that while my grandmother is from Hungary (my theory) that given the recent (then) fall of the Austro-Hungarian empire my grandmother may have been confused about where the actual border was?
Nevermind! Found an article saying there was a Soviet occupation zone in Austria until 1955- my mom was right!
besides, you may safely assume that ppl in that time have indeed had a distinct understanding which nation they belonged to and within the boundaries of which state they found themselves in. as a result of the Paris peace treatises, new independant national states were formed on the territory of the central powers, mostly in regions that have been historically multiethnical. not for long: the years between the two wars have seen the surge of fascistoid regimes all over europe, resulting in increasing ethnic separation, state oppression towards ethnic minorities and a whole new objective for foreign policy: ensuring the prosperity of regions with large numbers of expatriots. it was dangerous to refuse to "decide" which nationality one felt most inclined to.
also, austria-hungary is not particularly switzerland or canada. the union only lasted for roughly 50 years and was a powder keg only waiting to explode, over all its existence. for reference, just look at other once Austro-Hungarian territories, that have been part of (recent) larger unions: Slovenia, Chekia, Slovakia, Croatia, Ukraine --- i trust in these countries there is no confusions about the actual current borders.