How plausible would it be for the United Kingdom to offer the lands once New France to France in a peace treaty after the Treaty of Paris (1763) I am particularly wondering if France won a war in Europe in a 1770-1820 time frame. Thank you.
France could have had Canada, Eastern Louisiana (Mississippi to the Appalachian Mtns.), Dominica, Grenada, Saint Vincent and the Grenadines, and Tobago OR Guadeloupe, Martinique, Saint Lucia, and Gorée in 1763. France chose what seemed to them at the time to be the more valuable real estate. The door to French possessions on the North American continent proper was securely closed after that.
Well, that's not quite true - they did briefly regain the western part of Louisiana before deciding to sell it.
The Marquis de Lafayette also wanted to invade Canada during the American Revolutionary War, although this did not come to fruition. The French navy was in stronger shape then than it had been during the Seven Years' War, so it's conceivable that France could have retaken Canada if it had really set out to do so - but it doesn't seem to have been particularly interested.
France could have had Canada, Eastern Louisiana (Mississippi to the Appalachian Mtns.), Dominica, Grenada, Saint Vincent and the Grenadines, and Tobago OR Guadeloupe, Martinique, Saint Lucia, and Gorée in 1763. France chose what seemed to them at the time to be the more valuable real estate. The door to French possessions on the North American continent proper was securely closed after that.