I talked to AA and they agreed to change or refund the ticket. But it's the last flight of this day - so I would have to stay a night near the airport, fly to MIA the next morning.

Yes, it's 2 tickets and the AA ticket is CUN - MIA; MCO - MIA - SXM. I was worried to lose the complete ticket in case I can't make the first flight. The lady of the AA call center said in case I would show up in CUN late, can't reach the flight, they would put us on the next flight (waiting list) and I wouldn't lose the complete ticket.