Hmm. Could they legally kick Hungary out of Schengen without its approval?
Agreements outside of the EU framework - now that is indeed a clever workaround. I seem to recall similar maneuvers during the Greek financial crisis when the UK wouldn’t agree to things.
So I just answered my own question. I was confused by this,
Because I thought the Safe Third Country Agreement allowed them to be sent back with no right to be heard for asylum (unless they stuck in and evaded detection for 14 days).
However, according to https://www.wilsoncenter.org/blog-post/safe-third-country-agreement-expansion-causes-asylum-seekers-explore-new-routes
So I guess to get into Canada they’d leave the US and fly in from another country somehow.