Really? Come on. You can't give up that easy. What if the colonists had kept a complacent dogmatic attitude? We would be subjects of the British Crown. Nothing against them just trying to illustrate a point.
Your point being that you ought
to give up? Honestly, that's a terrible example. If it hadn't been for the American rebellion, British rule might not have been challenged in India, and France would have avoided the financial crisis that precipitated the French revolution (the reason that France was bankrupt was that they'd spent all their money fighting the British on behalf of the colonists in America - first their own colonists, and later the British colonists engaged in rebellion against the crown), thus avoiding the Napoleonic wars which devastated much of Europe for several years.
The Crimean war would have been unlikely to take place against this background, and there might have been a lasting peace in Europe once the American situation had been settled - this would have helped stabilise alliances within Europe, and due to Britain's treaties and trade with various nations usually at odds with one another, conflicts leading to the network of unstable alliances that gave rise to World War I could have been avoided (with British and French naval power in the Mediterranean and the land armies of Britain, France and Germany acting as peacekeepers).
The prevention of World War I would naturally eliminate the build-up to World War II, meaning that this conflict along with the holocaust wouldn't have happened. Post World War II American and British interference in the Middle East is what destabilised the region, meaning that radical terrorism might not exist today either.
So there you have it. Not giving up on the American Revolution is what caused 9/11.Disclaimer: Before any Americans get upset, it may be that I'm not entirely serious here, and that I'm simplifying a very complex set of geopolitical circumstances for the sake of a joke. Possibly.