Question

what were the justifications of the american revolution

Answer 1

If you browse over the transcripts here it should cover things:
http://education-portal.com/academy/topic/the-road-to-revolution-1700-1774.html

And the videos are short if you like hearing it.

Answer 2

When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation.

We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.--

This is the opeining of the Declaration of Independence and is probably what you are after.