The British refused to allow the Americans equal representation in parliament. Say what you want about "paying our way" for the war fought on our land, that's fine as long as we are then EQUALLY represented in parliament. The distance between the colonies and England certainly contributed to the war, but so did the King's-and the English in General-condescension, patronization and disdain for the colonists. There were a lot of factors, but it takes two to tango. The Americans wanted a fair shake, to be on equal terms with the British, and the British felt they didn't deserve it and were unwilling to recognize American equality under the law.
Today's America is a far cry from equality under the law, especially by our government. US governments openly flaunts it's contempt for rule of law, which has snowballed since Nixon was pardoned. It is now commonplace for American officials to not only break the law, but admit to it and justify it with obscene interpretations of constitutional authority.
History is history. Americans wanted equality with the British, British didn't want to give that concession. That was really what made war unavoidable.
As far as the Boston Massacre, the British were scared, but they were wrong for gunning down unarmed civilians. But John Adams defended them because of his reverence for equality under the law. He was truly one of the America's greatest. He would be disgusted by the way the law is twisted and manipulated and ignored today.