If I recall my history correctly, when the organization was first being set up, the Americans realized the makeup (of what was then the G6) consisted of them and all the others were Europeans plus Japan. The Bush [Bush #1} Administration decided adding Canada would give them another reliable vote, so the US wouldn’t be embarrassed by being a constantly outvoted minority of one.
Given recent history and the degree of alienation resulting from the Trump years, it seems unlikely that the US would want to risk losing a reliable vote within the organization.