If you have at least $2k in new spend on the statement with the return, I really doubt AMEX will care, there's nothing for them to clawback in the net. That will ding your threshold level for the next year though I would think.

Where I live, there's an easy answer this time of year for these things, I have to pay my property taxes in the next week and that's several thousand that I could pay a 2.75% fee to pay with credit card (though I'm not this year, don't need the spend), do you have any taxes you could pay, maybe even pay some federal income taxes?