The president could tighten federal oversight of the tech titan’s businesses, even if heavy reliance by the Pentagon and NASA on them makes terminating Mr. Musk’s contracts less feasible.

The broken alliance between the President and world's richest man could threaten Musk's lucrative pending -- and future -- federal subsidies.

Below is a list of U.S. regulators who oversee Musk's companies, including automaker Tesla, rocket and satellite company SpaceX, brain implant company Neuralink, social media…