Originally Posted by BHammy

No experience with WN or Canada or AA - don't fly them or go to Canada, but I'll venture to guess that WN has no connection routing at it's international destinations as they use direct routing methods.

Do a simple Google search: "layover vs stopover" and you'll find plenty of (recent) sites that indeed define international layover allotment of up to 24 hours: past that, it's a stopover. Most also confirm that domestic layovers are 4 hours, but possibly airline specific.

What stands out specifically is this one:
"Stopover: An intermediate ticketed point within the fare component at which the calculated elapsed time (the period between the scheduled local times of arrival and departure) is greater than the time period defined in a carrier's tariff as a stopover (4 hours for US/CA Domestic Fares and 24 hours for International Fares). A stopover is always a transfer."

And Wiki: https://en.wikipedia.org/wiki/Layover

So, yes, it appears that Canada is enveloped into the "domestic" schema.

But when it comes to Delta baggage, I know I've pushed beyond the 4 hour window (at a domestic airport, on international itinerary) and have the capacity to push to 24 hours at international connection points (sans Canada)