First, the RISC-V Consortium is an organization (now) based in Switzerland. Second, there is literally nothing anyone can do to stop you from making a RISC-V core, short of calling it "RISC-V". For that, you have to pass a few tests, but all trivial stuff for a serious contender.
On a related note, I don't think it's an accident that Apple almost completely avoids talking about "Arm" but instead calls it "Apple Silicon".
Is it possible the USA government can say that this is open source and free for all to use, except for people in China.
For example, if Red Hat Fedora is open sourced, but Red Hat is a USA company. Then they will still be under USA jurisdiction.
Given all the lies and bullshit coming out of the current administration, I can actually see them doing this.