How directly was he involved in the negotiations? Often the king is the ultimate authority in a country, but they don’t actually make many decisions themselves.

It’s well known that the colonists were looking for a reason to break away, and that the taxation issue was a convenient excuse. After all, taxation without representation was the norm. It wasn’t like all of England had the vote and had representatives in parliament. Entire cities had zero representation but were still taxed. Ireland had been part of the British empire for ages and it didn’t have representation.