Krugman has this to say about it:
For those not familiar with how financial markets work, US Treasuries are the ultimate safe asset, used as collateral for everything. Even a hint that some Treasuries might not be honored could bring everything to a screeching halt
Musk and Trump are both in the habit of stiffing people they owe money. If markets even suspect that this habit will extend to Treasuries, God help us
If you mean he is working for them… nah. He wouldn’t do what they ask, or would screw it up. They get smarter people to manipulate him into doing things in thier favor. I suppose that could be called a foriegn asset to. Not sure though.