Maybe terrorism and terrorist are oversimplifications of reality, because reality is that in almost any conflict there are bad things that happen from both sides, but the critical point is can one see a basis for the outcome that makes sense to the person applying the label ?
In the case of the Native Americans vs European expansion, for the most part I think both sides were in the right, on balance, both sides commited atrocities, and eventually one side got the upper hand. But not entirely, because in many of the ways the United States is different from Europe, it's because of the adaptation of native American culture by Europeans into what is the American culture.
Likewise in Palestine/Israel relations, both sides have some valid points, and some invalid points, the largest invalid one being a kind of anti-semitism coupled with general religious intolerance on both sides. History has shown time and again that killing each other over religion is a fruitless exercise, compared to killing each other over more valid principals like liberty, or democracy.