This is a large part of the reason I do not consider myself a pacifist: I cannot envision human history up to the present without the presence of war. Perhaps that is a failure of imagination on my part.
However, I still hold that war is not something that we can justify or condemn; it is too vast for the individual human experience to account for. Perhaps we can justify or condemn it historically, such as you present with the American Revolution, but if we speak of morals, or simply of the human being's ability to come to terms with war--there I think that war (like history, like fate) extends too far beyond us to be answered for. We are aware of its presence and must try to survive it.
I don't know what would've happened had America not fought Great Britain, nor does such speculation much interest me. I think the American leaders put forward and defended some radical and noble ideas, and Great Britain was compelled by political forces and a somewhat mad king to oppose them. In regard to motivation, I'm inclined to the Americans' side, and historically I think the results of revolution were very important and in many ways beneficial. The war itself I have no comment on.