Is the AA schedule change significant enough that you'd qualify for a refund or reissuing of the ticket to a later flight? I would never trust this connection given that:

1) CUN can be a zoo that time of day;
2) Cubana's punctuality leaves much to be desired;
3) this is obviously on two separate tickets;
4) these two airlines have no way to communicate with each other;
5) you'll have no way to communicate with AA in the event of a delay.