The free market is usually predicated on rational actors. I don't think the target market of teenagers fits the bill, nor does any market, really, once propaganda enters the picture.
Google and Apple have publicly stood up against the US government, and the US doesn't (publicly and legally, at least) meddle with companies to anywhere near the same extent as China.
When I support Google, I support Google alone, but when I support Tencent, it feels a little like I'm supporting the Chinese government, too.
The problem is that the Chinese government has almost total control over Chinese apps, so American citizens are rightly afraid that Chinese apps might serve as vehicles of Chinese government propaganda.
It's totally okay for both America and China to ban whatever foreign stuff they want, though, and both of them have very good reasons to do so.