There are a large number of existing auto JVs, and I'd bet that it's not much like an aircraft company, where it's completely normal to order a jet engine from

There are a large number of existing auto JVs, and I'd bet that it's not much like an aircraft company, where it's completely normal to order a jet engine from a different company than the plane manufacturer. And jet engine technology is subject to export controls. I looked at the GM JV situation, and it appears that they do manufacture engines in China.