As I have said before - The main effect of a failed 1787 Convention - is the calling for a 1788 convention.
Whey need to know a little about How/When the Convention Failed.
How much of the OTL Constitution had been Proposed/Agreed on. And what was the public debate over the proposals, after the Convention was over.
This is what will determine the Blocs the States eventually form
Assuming you really mean ?WI the AoC hadn't been replaced, and the Union Failed?
Just because the Convention Failed the AoC doesn't disappear over nite.
When did the AoC collapse, before or After Vermont, and other states joined.
?How did it Fail/Collaspe?
I see Blocs forming/reforming and operating as Independent, while the States send Delegates to a increasingly powerless AoC [just like OTL's UN]
You need to look at the wording of Virginia's relinquishing of it's western territories, & The Wording of the NW ordinance, For whether Virginia and the other southern states can continue/resume their claims.
While Pennsylvania may be able to push claims into the Ohio, I doubt if NY and the NE states will bother. After all they are blocked by Canada and the Lakes.
New England will continue it's Maritime development, Taking over the paying of tribute to the Barbary Pirates. Different or No Barbary wars.
Also No treaty with the Kingdom of Sicily for Basing of Our Ships.
It will also be competing/associating with Britain for the Spanish America Smuggling Trade [Any non Spanish ship involved in intra SAm shipping is considered Smuggling]
?Does this lead to better or to worse relations with Britain?
Whe have the Quasi War with France in 1798, A more unified Maritime New England May may push for a real war, with The rest of the AoC resiting.
this may lead to NE negotiating the Equivalent of OTL's Jay's treaty.
Do whe get the 1795 treaty with Spain opening New Orleans to American goods. and relinquishing Northern -West Florida-
And What is the reaction to Spain's reclosing the Port in 1798. OTL the US was able to pressure the reopening in 1798, and again in 1802.
?Can the AoC apply the same kind of Pressure? If the AoC has collapsed can the Replacements combine to apply the Pressure?