I'd say the policies of the current US administration might have a part to play in it, with continually increasing friction at the border, 51st state talk, and the tariffs. No FUD necessary.
I live a short drive from the border and would make a few trips per year usually. I've met a lot of good people in Montana & North Dakota. As it stands I haven't been to the US for over a year now, and don't care to go anytime soon. It's easier now to just stay here and spend my money locally, rather than in a foreign country.