My experience of late is that AM will float absurd changes if they cancel a flight - like leaving a day early in a lower class of service - but telephone agents do their best to sort it out. And they answer calls quicker for those with no status than Delta's Diamond Desk answers calls from elites. AM's own lounges are poor but the Centurion lounges in MEX make up for it if you have access. Expect plated options from the latter rather than a buffet. Afternoons and evenings are best for avoiding immigration crowds at MEX.