One big difference, is that the opposition to nazi Germany was relatively weak before the start of WW2:

After Reginald Drax's mission to Moscow failed, the Soviet Union ended up signing its famous non-aggression pact.

Italy was allied, Spain was neutral/aligned. Turkiye was neutral.

Poland could only count on UK and France[0].

Compare to now, where the NATO military bloc is massive. No one would dare risking a military confrontation in these circumstances.

If anything, when there are any tensions between two non-NATO countries, it makes it more urgent for one to oppose the other joining NATO (attacking before they'd join NATO would stave off them joining, attacking after they'd join NATO would lead to an unwinnable fight).

0: https://en.wikipedia.org/wiki/Anglo-Polish_military_alliance

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