How about we make this a less major POD.
Washington reacts to the flanking, the Continential Army stands it ground but is forced back in good order and contuines to block Howe's line of march to Philadelphia. How Howe is forced to decide just how many casulities he's welling to give for Philadelphia, against what is starting to look a european (abed a 2nd rate) army. Add this to the events of winter, when Washington proves himself an unconventitonal stragist (opposing commands hate those almost more than being outnumbered.)
So (POD) Howe decides to adandon the Philadelphia line, either turns and heads of Annapolis or goes back to New York (far to late to salvage anything from the Canda-Hudson campaign). Afterall Howe is a Bunker Hill witness, and a Whig (and early war opposer). Routing Washignton around New York and taking New York hasn't worked, would a grinding campaign to take the capital?
So as has been state France enter at the same time BUT prehaps with real force far quicker. And Howe eventfuly has to abandon Annapolis and return to New York (if he haven't already) makse for a far more Public defeat (British run for New York because the French are coming than the OTL withdrawal accross New Jersey.
I think in this scenerio the war ends (all of about give the Whigs (the Fox brothers my favorite British pols) enough to bring down the government) and peace comes in late 1778, early 79, sorry not 77. I suspect the big impact would be less justification for US team in Paris to demand the west terrorities. AND less credit to France, and a quicker healling between the US and Britain.
** One note, Bendict Arnold ends up the 2nd greatest American, Commander of the Army when Washington turns in his sword (2nd greatest moment in American history)