I understand that U.S. Congress passed a law in 2011 barring space agency collaboration with CNSA because of concerns over "national security".
I also get that China blew-up one of their own satellites causing a massive distribution of orbital debris, which was understandably unpopular.
But other than that, is there any real, solid, practical reason I'm missing, besides just politik? (would be perfectly acceptable answer if so)
Not inviting China to the ISS means China is now building their own space station, the Tiangong, so if the worry is "technology over-sharing", well, they're already replicating most of our abilities already. (China's capsule, the Shenzhou, looks like the design borrows mostly from the Soyuz anyway.)
Are we in a cold war with China? The U.S.-Soviet cold war did bring a truly exciting pace to space exploration, even if we were duplicating each others' work and spending unprecedented amounts to do so.
The issue is, a ticket to Mars is very expensive-looking on a politician's budget review sheet, so while they don't want to be the ones who say "no," I'm sure they'd welcome support from countries willing to share a chunk of that price tag.
Side Note: I've also just learned that India is not part of the ISS program either? This is even more strange, because it seems to me like they've had more launches per year, more successful missions, and their PSLV has come along nicely and is looking impressive, even though the ISRO isn't as "big" as China's. Plus, I don't recall US having any major political beefs with India. And I'm sure they'd love to go to Mars with us.
So, why does the "International" Space Station seem to wave a "Members Only" flag?