How would an earlier confrontation go?
The Stamp Act wouldn't cause open war by itself, but the colonies would continue embargoing British goods in response until something snaps. If the British respond by cutting off the colonies' trade, war is likely. Although you need a British prime minister willing to dive into this, and up until Lord North I don't think any of them were, though of course I can't say exactly.
Revolting at an earlier date probably wouldn't be good for the colonial side. It would be ten years less development for colonies that are developing very quickly. Although, there may not be a full-out revolt at all. That's a hell of a short time period from going from very good relations with the British to bad enough relations to declare independence. In OTL they had 10+ years of mounting hostility. Hmmm.