I think this is probably legal in the US, since most employment is "at-will," meaning both parties can terminate it at any time, for any reason, or for no reaso

I think this is probably legal in the US, since most employment is "at-will," meaning both parties can terminate it at any time, for any reason, or for no reason at all (with some specific exceptions that probably wouldn't apply in this case). Your employment contract may have terms that override the at-will relationship, in which case the employer has to follow the contract's terms. You may also be unionized, in which case the union will have negotiated termination procedures with your employer. And you may live in a State that has additional rules for terminating contracts. But as a general rule, I believe this is legal in the US in most cases.