回复：求助"车祸索赔",在美国,多谢!

The gist is that how you make sure the guy was working for either company A or company B, AND, when the accident hapened, what thus guy was doing. Assume he was on a business trip, then both companies will be vicariously liable for his conduct, if he is working for either one of them.
In this case you'd better find out who he is and sue both him and the company in US federeal court in your jurisdiction. To me, his conduct is wilful and reckless so that a punishment penalty is very appropriate.