The contract is completely valid--the fact that you are not an American does not make you exempt from ordinary American law, any more than the overseas supplier of an American company can claim that they are not bound by a contract because they are not from the U.S. And even more so: according to the language you quoted, you specifically agreed in writing that 1) California law will apply, and 2) if there is a disupte, it must be brought in a CA court. Those provisions will be enforced against you. Mind you, if you remain outside the U.S. , even though you can be sued and a judgment obtained in the U.S. against you, it may be very difficult for the other party to collect; they would have to try to get your local courts to enforce the U.S. judgement. Many nations will, but not all, and it can be expensive and time consuming even when possible.