That's a weird pull. AFAIK the MPEG group is international. Broadcom, AFAIK, is the biggest pusher of VVC and they are American.

Anyone can participate, yes. For H.266, many of the big H.265 contributors didn't participate as much while Huawei, Tencent, Bytedance, Alibaba, etc. stepped up their contributions significantly. The bulk of the new coding tools were developed by them I believe.