Check with your insurance company to be certain, but generally in the U.S., the car is insured for any driver that is using it. (In the U.K. it is the speciific driver who is insured.) If there is an accident caused by the borrowing driver, your insurance company would be responsible. I’ve never heard of anyone who is borrowing a car getting pulled over and accused of stealing it; unless there are very bizarre circumstances, I wouldn’t worry about that.