It's been years since I've seen them movie but I recall having a third interpretation of the joke.

I thought Austin has assumed the communists won because prior to being frozen he felt that USSR had a stronger standing in the cold war and would be the more likely victor, regardless of Austin's personal opinions on communism and capitalism.

To expand on this, you could also imply that Austin assumed the capitalists lost because he was frozen. He knows he's a great spy, what chance did capitalism stand without him fighting for it?.

I don't intend to rewatch the movie because my life experiences since then have made it impossible to enjoy media that uses homophobia and transphobia as common punch lines, but I can still agree that it's a great joke, a great movie for it's time, and cleverly written.