Dude, there must be something incredibly specific about this case for this to be a thing. Like the wife just said she was a tourist and never left instead of applying for a green card.

If you just do the paperwork - enter the US under a K1 Visa (fiancé(e) visa), get married, and then apply for a green card once you're married - you won't be randomly deported when your spouse gets leukemia.

It is actually is very easy (multiple people in my family have done this - one guy has even sponsored multiple foreign wives because they keep leaving him cuz he's an asshole). But you do have to do the paperwork if you don't wanna get deported.