Czechoslovakia then ceded territory to Germany, Hungary, and Poland while under threat of military attack by each of them. By the standards employed in this thread, Poland "allied with Hitler".
in 1938, that's exactly what Poland and Hungary did: ally with Hitler to seize territory.
Yet of course, the actions of the USSR towards Poland go way beyond anything Poland and Hungary did in 1938. Not merely building up forces on the border, but
actually invading, with a treaty promising territory and assistance to Nazi Germany. And updating that treaty with additional territorial promises and practical aid to the Nazis into 1941. Providing the Nazis with over half their imports and heaps of war material. Offering to join the fucking Axis.
And to counter this, you have a counterfactual scenario in which the USSR comes to Czechoslovakia's aid. OK, but it didn't happen, and they pivoted towards the Nazis to realise their territorial ambitions. That's the scenario that actually played out-- with heaps of Soviet assistance to the Nazis, fuelling their war machine for years.
By reasonable sane standards, those that practically assist the Nazis with their territorial seizures are "allied with Hitler" as long as that assistance lasts and until they stand against them. Uhrm, yes, that's uncontroversial. Poland and Hungary allied with Hitler briefly in 1938; the USSR allied with Hitler for fucking ages against numerous Eastern European targets and aided them against the allies until 1941.
Whereas by your standard, the USA isn't allied with Israel.