At this point, seeing as the next summit is in Canada anyway, they should rescind the United States’ invitation to the event.
Then it would be nice if Canada and the other five nations formally announce that they’re booting out the US. And maybe invite in some new liberal democracies, like the Nordic countries, New Zealand or South Korea for example.
Meanwhile, MAGA-land can go off and form their own new G-whatever with Russia, Saudi Arabia, Belarus, Hungary, Argentina and whatever the fuck other countries they can round up that are run by fellow fucking ghouls.
My hopes for this fantasy scenario are low, though. I don’t really have any expectation that our fellow democratic allies will make any significant moves to stand up to the US or take Canada’s side in a dispute with the US.