Here's OTL backstory, this paragraph all is actual real events of OTL-the US Constitution need 9 states before going into effect. Until then the Articles of Confederation was still in effect. In fact the Confederation Congress was still meeting while the Constitutional Convention was meeting, and had been ready to admit Kentucky as a state per Virginia having finally voted for the go ahead, but Congress didnt want to cause legality issues if the US Constitution were ratified and Kentucky wasnt godfathered in. Rhode Island had not attended the convention even though they were one of the main reasons it came about, they were leveling taxes on good passing from MA to CT through RI pissing off MA. RI in fact was last of the 13 to vote yes.
Now we get to ATL , inspired by Brexit and the British reluctance to move quickly, my question is- say 9 states vote yes and the Constitution goes into effect. RI (or all of the last 4- NY, VA, and NC) dont ratify, but say "we never left the USA" and try a limbo of being collective security with Constitutional USA, similar to EU having some countries but not all in Schengen Zone or the Euro Zone. Kentucky and Vermont may even choose that path as well. Analogy- those states may have a similar relationship to the Constitutional USA as the Isle of Man has with the UK.
Plausibility? If RI (or more) try that, consequences? How does history play out?