But, I think there some unique things worth seeing for an American: The old parts of Montreal/Quebec city, and the Alberta Rockies, especially the corridor between Banff and Jasper.
Like, if you want to see a rain forest or a thousand year old Buddhist temple or a pyramid, there's not really a substitute in the continental US.
But if you've two options, where you can go to the pretty good option domestically or drive past it and continue on to the much better option in another country ... most people will be happy with the closer option, even if there's some small number of people who want the best or have seen all the closer options before and want something different or just whimsically like the idea of going to the further-away one none of their friends have been to.
Minor nitpick, but there are temperate rain forests in the continental United States. What we don’t have are tropical rain forests.
I don't know about "exotic", but for anyone living in the northeast of the US, the easiest way to visit Europe (sort of) is to drive up to Montreal/Quebec.
Having been to Europe, no comparison.
Nothing prepares you for walking along a city street then “oh fuck, a castle…” and learning that it is now, the city’s government building. Cool… (Stuttgart, you’re awesome)
If you go south you get sun and beaches. The coastal regions of Canada will be comparable to the coastal regions of New England and the Pacific Northwest, so there's no need to go all the way there if that's the sort of beach you're looking for.
Likewise your outdoors, your cities and restaurants and museums are all going to be about the same as the options available in the US, just further away. It's not really "exotic".
We don't really have the same emigrant relationship with Canada; my grandfather's family spent a couple generations in Canada, but my mother only found out about it after he died. He considered his family to be Irish and to have come from Ireland; that they came to the US via a couple of generations spent in New Brunswick was never a part of the family lore.
So there's no real "visiting the home of my ancestors" sort of feeling you'd otherwise see.