OOC: Washington's rebellion? Hmm...
IC: Well, maybe if he hadn't declared himself King of America and all that. What you all seem to forget is that, not only did they get foreign support (from France - this was during the Seven Year's War, remember), but they actually succeeded in driving the British out for a little while.
However, Washington was declared king by his soldiers after his victory, the "Congress" that was the rebellion's civil authority decided it didn't like that, and they fought each other for a while.
It wasn't until after the end of the war that the British retook the Colonies, which by then had been reduced to smoldering ruins by the civil wars and were grateful to be taken back into the fold.
Though I wonder...
If Washington hadn't rebelled against the Congress and they had managed to establish a functioning state, they would have been far better positioned to take advantage of the Great Plains than any European power.
As a revolutionary state, it would as a matter of course welcome dissidents from other nations - such as the ringleaders of the failed French rebellions over the next few decades - and it's population would steadily expand and push west.
Of course, it would probably collapse from internal differences, but before then, who knows? They might have even reached the Mississippi!