Most likely Puerto Rico if one ever happens. I think there have been votes on it a few times. Part of Canada also took a vote to become part of the US maybe a decade ago? It might have been longer.
Puerto Rico should never become a state. Its economy is almost 100% tourism-driven and its population is shrinking by 1% a year. It would be terrible for the country.
As others have said, Israel is pretty much a de facto state of the U.S.
I wanna learn them all like right now.
