I have to confess total ignorance on this one...
Given the OTL starting conditions, were there any battles where different leadership or weapons or something could have turned the outcome? I've seen a claim for King's Mountain being winnable, had Ferguson rifles been in play. Anywhere else?
I'm willing to accept any reasonable change after the war begins, including adding U.S. allies (Spain or Holland?), weapons (like the Ferguson, anything in trial or limited use, or a prototype that gained official attention), & such (a leader falling off his horse & breaking his neck when he lived OTL, or taking a bullet when his horse got it OTL, I'm fine with).
As for "decisive", if the U.S. still wins but France loses territory, or the Brits do, that didn't happen OTL, fine by me. (Less interesting is a U.S. loss, but if that's how it goes...

)