American History

Economic. The king's treasury was surely being depleted. Loss of commerce between the colonies. Remember, part of the cause of the war was British East India Tea Company was taking a hit and they wanted to make it up in the colonies. Cotton wasn't being shipped to Brit mills.

Were upper class Brits gonna be taxed to continue the conflict?

Military. Loss of Saratoga and Yorktown were disasterous. Secondariiy, were the battles that weren't won by the Americans but weren't British victories, either: Brooklyn Heights, Monmouth, Brandywine, Springfield and on and on. Springfield is of interest because Georgie paid for Hessians to help defeat the colonists. They completely fucked up by attacking Washington alone. They were supposed to wait and join forces with a British force and then attack Washington. And they were expensive.

Morale on the home front: Not all Brits were in favor of the war.