The American colonies were too expensive, too troublesome and too far away. They ultimately just weren’t worth the effort for the British to keep. Trying to keep the American colonies under Crown control also never had truly widespread support even back in Britain itself.

The odds were just stacked against Britain. Despite having such a feared and powerful army and the best navy in the world, it was extremely difficult for Britain to keep their forces supplied over such vast distances. Also, British troops were also fighting on hostile. foreign territory totally unfamiliar to the average soldier which the Americans fully took full advantage of.

Also, besides fighting the French, the Spanish and Dutch merchants were also sympathetic to the American cause and traded supplies such as arms to the Americans and both were eager to weaken their historic rival in Britain, thus Britain couldn’t afford to fight multiple European powers in a long drawn out war.

Any serious efforts for the British to try to reclaim their former American territory would have ended permanently after the largely inconclusive War of 1812.