The American Revolution, if you took it apart, would probably a million causes. Nothing as big as armed rebellion, especially when successful, can be said to have simple causes. Despite this, it is possible to come up with a few overreaching situations that caused enough trouble to push people over the edge.
It is important to remember that not all Americans were in favor of splitting from England. In fact, in it was in some ways akin to a civil war. So the things that drove some folks nuts didn't bother others and that can cause grief when trying to definitely say what caused it. So take this list with a grain of salt.
- Taxes. Most Americans didn't mind paying their fair share of taxes (at least they didn't grumble about it any more than we do now) but they were very unhappy with the way those taxes were created. Americans, in general, wanted to have a say in how they would be taxed. To this end, they wanted to have representation in the British parliament. As a colony, though, it wasn't given that right and therefore new taxes came down without much input from locals.
- Local government. It took a long time for somebody to sail across the ocean to petition the government, so in the colonies many examples of local, elected governments filled the gap. Over time, the idea that folks "on the scene" might be better at governing things than people an ocean away gained traction. The King, of course, was not always happy with such a distribution of power.
- Meddling. The British government had its own agenda, and it didn't always match what the colonists wanted. For example, the government didn't want the expense of protecting colonists from the natives if they spread out too far across the country, so it created a law that kept colonists from moving past the Appalachian mountains. This territory had just been won from the French with some effort, and people were angry they couldn't take advantage of it.
- A unique population. There were people from all over Europe living in North America. Most of them left Europe for very particular reasons, and living so far away in "unbroken" territories had made many of them very tough folks who were used to being self-reliant. Things weren't as set in stone as they were in England in terms of your lot in life.
- Talent. The policies of Great Britain had alienated and irritated some of Americas best and brightest. These people, in many cases, also had the financial resources to cause trouble with but no aristocratic title to worry about losing. No revolution would have been possible without remarkable people to get it moving.
Overall, if I had to choose just one cause of the revolution it would be a very stupid King and stubborn parliament. Had they compromised on just a few issues the revolution wouldn't have taken place. Most colonists were not bent on independence from the beginning, but rather more "home rule" and a certain level of equality with the "old country."