> I suspect that geopolitics will leave US/China GPUs with largely non overlpping customer bases

That's not what's happening in the auto-industry, Chinese EVs are easily outselling American ones. Why would GPUs be any different?

Import bans, like we have on Chinese EVs in the US. The US already restricts other countries access to Huawei hardware

This is another example where we might ask "why would it be any different?"