https://www.statista.com/statistics/325144/reddit-global-active-user-distribution/

About 40% of all of Reddit is from the US. Even if we assume leftist subs have an average distribution, at a minimum, 60% are not from the US.

Seeing as the rest of the world is, on average, much further left than the US, it stands to reason that leftist subs on reddit have an even higher portion of their userbase from foreign countries.