My thoughts about this are that there are (broadly) four groups of things behind the drop:
1). General antipathy to the US because of their threats to our country
2). Specific concern about travelling to the US because of security issues at the border, etc.
3). Low Canadian dollar - this is particularly acute relative to the USD, but we're also below the average of say the last 10 years or so for the EUR, GBP, and CHF, so hotels, restaurants, etc. are more expensive.
4). Economic uncertainty - if you worked anywhere in the auto industry (from raw metal to the dealership), the impact of a 25% tariff on your job security doesn't exactly scream "get the credit cards out!"
Because of 1, the airlines can't do a ton of promotion to rebuild the US market -- can you imagine WestJet or Air Canada rolling out the "Star-Spangled Seat Sale" right now? They'd be crucified. (Not a great time for WestJet to debut
Elon Musk's Starlink as a new in-flight perk.)
They can't do that much substituting travel to Europe -- firstly there's the low dollar, plus in general European travel is more expensive than a quick trip to Chicago or whereever and thus more impacted by uncertainty. There's also limited capacity at airports there but more importantly airframes -- if my read of the ranges in the Wikipedia articles is correct, WestJet has 138 airplanes, and only 7 (the Dreamliners) that can make it to London from Calgary. The bulk of their fleet, the 737-700 and 737-800 can make it to LHR from YOW (but not YYZ); their 43 MAX 8s can make it to LHR from YWG but not any further west. I think that WJ is hurt more by this than AC because their customer base is more in the west -- further from Europe.
So that leaves pumping up domestic travel, which is only hit by number 4.
