[gambiting]

I would say "being actively at war and shooting each other" counts as interaction.

[croes]

But is that a kind of interaction that leads to cultural exchange?

[gambiting]

Cultural exchange isn't what the parent post suggested though. More that a lot of modern American culture has emerged as the result of the war with Germany and Japan - popular comic book heroes being one of them. Capitan American beating up Nazis wouldn't be a thing if well, you weren't at war with the Nazis.