The fact that you are a foreigner, that you cannot find work in the US, etc. is really not a valid excuse - as there are many Americans in exactly the same situation. While having the credit card, you used it, and purchased good/services which you've used or are still using. In essence, you do not own those things because you have not paid for them.

If you skip out on the debts and you come back and work, more than likely the credit card company will eventually become knowledgable of that fact and take action against you in some form.

If you come back simply to visit, I doubt that you'd have any issues. Though, with the way all of the government computer systems are tied in to the financial world these days, who knows - they may put a notation in your passport record and when you try to enter the US in the future you may be surprised with what happens.