[Butch Cassidy Slept Here]

Sounds like the re-scheduled flight, from Miami to New York, gets into New York too late to make the connection to Montreal. So they opt for the Greyhound. Only the last Greyhound, for the day, to Montreal, has already left. So they spend overnight in the Port Authority Bus Terminal. For those who are not familiar with New York, an overnight at the Port Authority Bus Terminal is like staying overnight in the mental ward. I don't think the OP will be transiting the USA again soon. This also sounds like one of those cases where Mexicana, or American Air, offered a fare of ten bucks less than Air Canada. Air Canada is no better than American in terms of how they treat their customers. The only difference is Air Canada is, by (Canadian) law, obligated to have staff that can speak French and they would have no connecting points in the USA for flights from Latin America.