Was the American revolution a radical or conservative event?

The answer to this question is subjective. Either answer can be adequately defended, and neither answer is more correct than the other. Additionally, "radical" and "conservative" are subjective, relative terms. What is radical for one person might not be anything close to another person's definition of radical.
Personally, I feel that anytime a group of people decides to overthrow a governing entity by using violence against that ruling power, it is quite radical. I generally consider violence to be a last resort option. The normal, "conservative," and/or political strategies have failed, and the only remaining option is violence. That's a radical step because thousands of lives would have been spared had the revolution not turned violent. America might be a very different country or maybe not independent at all, but saving lives is an admirable goal.
On the other hand, I suppose that staying passive and letting the British government dish out legislation that didn't aggressively care for the colonies could be considered the radical option. The idea of getting slapped and turning the other cheek is quite a radical idea to many people, so fighting back is the conservative option.

The American Revolution can unquestionably be labeled as a radical historic event. Radical in this sense, and according to Websters Dictionary, meaning "favoring or resulting in extreme or revolutionary changes, as in political organizations". In this respect the American Revolution was completely radical. The vision of the founding fathers, as outlined in the Declaration of Independence, was to secure freedoms and liberties for the people of the American colonies which were actively being denied by the British Empire. By simply writing this declaration and sending it to King George III, the American colonies set in motion the most radical phenomenon of the day.
Furthermore, these colonies were now determined to abandon monarchial rule and govern themselves. Through this revolution the founding fathers and the American patriots who fought for it, were able to overthrow British rule in the American colonies. In 1783, the American people were victorious and broke free from the parent stem of the British Empire. This event was unprecedented, never before had a colony overthrown a monarch in order rule itself. The American people went on to develop one of the first true democracies in the world, another radical idea in a time dominated by Monarchs and Empires.
The American Revolution was an open act of rebellion against one of the most powerful empires of the day. A group of colonies banding together and declaring war against their monarch was the epitome of radical in the 18th century. Aside from the war itself there were radicals throughout the colonies. The "sons of liberty", responsible for everything from smuggling to tarring and feathering loyalists, would most definitely be considered a radical group. The revolution would serve as the spark to ignite further insurrections across the globe. Although it may not have been the most violent or sweeping in its scope, the American Revolution was far from a conservative affair.

To some degree, the American Revolution was radical, as the American colonies revolted against a great imperial power. The Declaration of Independence enshrined the ideas that Americans had the right to "life, liberty, and the pursuit of happiness" and that these were "inalienable rights," or rights that could not be taken away. The revolution was the embodiment of the ideals of Locke's social contract theory, and the new United States would become the closest thing to a democracy since Athens in ancient Greece.
However, the revolution was less radical than revolutions such as the French Revolution and the later Russian Revolution. The American Revolution did not change the status of slaves, who remained enslaved, and women were not allowed to vote. For these reasons, the revolution, which also preserved existing property rights, was somewhat conservative.