Newfoundland was once its own separate Dominion, but came under direct rule of London again during the Great Depression when it was unable to handle the debts from World War I. After World War II, the island hosted several large US military bases and the economy was booming. There was a vote in 1949 whether Newfoundland would remain governed by a London appointed commision, return to independence, or join Canada. The Canada result won, but only with some dodgy undertakings.
If the independent vote succeeded, then Newfoundland would likely move to some sort of free trade and customs union with the US. That was the platform of the independence party. If that happened, it's possible future integration might occur with a common market and later Newfoundland even using the US dollar. Given enough time, Newfoundland might even apply for statehood. That is a low of "ifs", but its a plausible path for Newfoundland to join.
Another possibility is that the US negotiates harder with the British during WWII and possibly gains British Caribbean islands rather than just bases in which case the British Bahamas and some of the Lesser Antilles might join the US Virgin Islands as US possessions. I believe Bermuda is too valuable a naval base at the time for Britain to give that up, and other possessions like Jamaica, Belize, or Guayana too major. But some small islands might be worth it.
Okinawa might have been made a US possession after World War II, but if so then Okinawa likely becomes an independent state after the 1970s like much of the US Pacific dependencies.
It's also possible that the US could have negotiated something with Denmark that saw Greenland become part of the US after World War II. I believe the US offerred Denmark $100 million to buy it in 1946, but Denmark said no. If this happens, Greenland might remain part of the US given its strategic importance, but the US would probably allow extensive home rule. Population would be too low to ever make a state. The population might be US nationals, but not US citizens. Or they could be full citizens with voting rights. It depends on how things play out.
These are the ideas at the top of my head.