I would indeed say that Washington barely qualifies as American - he certainly thought of himself as British until after the revolution, with a lifelong ambition to serve in the British Army. For a start, unlike the independence movements in Brazil or the Netherlands, the Americans did not originally go to war to secure independence; they saw themselves at the time as revolutionaries in what amounted to a civil war, and used terms like 'Rebels' and 'Revolutionaries' for themselves. Not that many self-declared as 'Americans' as a perceived identity separate from the British. They called their conflict the American Revolutionary War and didn't adopt a declaration of independence until the war had been ongoing for a year. "American" in this context referred only to a geography - it wasn't a national identity any more than "Home Counties" or "East Anglian" is in the modern UK.
There is something vaguely annoying about this.... It's almost as though you have filtered the facts to come to conclusions that you find palatable.... But that's OK that's your perogative...
I'm sure to the extent historians can actually interpet this stuff, Washington would have had a number of "loyalties"....to his "British"...probably better to say, English ..heritage... To the American colonies of which he was a product.... To his immediate family and its interests... To his own own business interests.
But the indisputable fact is that when the provocations from the British crown became serious enough, he threw in his lot with those who felt the only option was to separate from the "old country" and form a new nation.....I'm sure all of those founders had plenty of misgivings and forebodings, but they took the plunge anyway.
It is interesting, though, and similar to what you would expect today....the majority of the colonists were either opposed or indifferent to the revolutionary cause....and a high proportion actual left...likely at least in part, because life became intolerable for them in the new nation.
But to say Washington was British and not American...or just barely American... sounds like "tetrapyloctomy" to me. Once it was clear there was to be a new nation....then he was definitely an American.....
And to imply that the American colonies were not much different in terms of "identity" than the Home Counties or East Anglia, particularly by the time of Washington simply seems mischievous..... [Oh yes...I might grant you Yorkshire though...it has always seemed a bit of a "reluctant" part of England to me... and, of course, there is the Isle of Man which although it definitely seems to be part of England, isn't...nor is it even part of Great Britain.]
BTW...I am NOT an American....