Very risky idea. If you don't already have the IR1 visa, it would be best to postpone the interview, so your contract is over before you enter. Your plan plays fast and loose with the rules, even if the US Citizen is in the USA or enters with you. If the US Citizen is not ahead of you or with you, you will likely be denied entry. You can try entering again before the visa expires, but trying to do things against the rules is a crazy risk. Play it straight or don't play, is my advice.