What happened if washington lost the war of independence

Two things here: first, the majority of "Americans" (most of whom, at the time, considered themselves Englishmen) wouldn't care. More than half were unconcerned either way, and a large number were devout loyalists. About a third supported the rebels, but of course the actual "hard core" of rebel support was much lower. I imagine the majority of the rebels would simply move to a new town and never reveal the fact they had participated, and a few, the hard core, might flee to the wilderness. Among the more prominent, a few would be executed, the rest would be pardoned after washing their hands and being suitably shamed but in general they'd get off light (they were, after all, English aristocrats and leading merchants). They would not flee west, if the French were allied with the British against the rebels, since the French and their native allies would be in (nominal) control of that area at that time.

No. The French in North America had a very small presence by comparison to the English colonies. If they were going to attack the Brits, it would have to be done with forces brought from Europe, so whether or not they had Canada wouldn't really make much difference. More likely, they would just try to secure that border and land in Nova Scotia and use it as a staging ground. To attack from Canada would be nuts - the French would have to pass through the lands of Britain's most ferocious native ally, the Iroqouis. That would be a whole war in itself.

The French weren't really interested in taking the thirteen colonies. Their interest in North America at that point was the fur trade, not conquest or settlement (beyond what was necessary to achieve control of the fur trade). The 13 colonies was an administrative nightmare, and who would want to take possession of a set of colonies that rebelled over paying for their own defence? There could be no profit in it.

If the Americans lost the WoI, there would be alot of natives in North America today. Most of the continent, would be populated by natives, with some French scattered among them. Probably these areas would have become adminstered colonies of France after a time, and eventually (probably by the early 20th century, at the latest) would have been granted independance. The West and Canada would look alot like northern Canada (eg northern Prairies or northern Quebec) does today, predominantly native. The 13 colonies area would be more or less like English Canada is today. Mexico would probably possess much of what is now the southern US, possibly even California. In general, the continent would be much less important in the world, but it would have a much less tragic history (especially for the natives).