Since we have changed our tactics, we have become very successful against terrorist groups worldwide, so yes we should keep it up. That being said, we must always continue the debate on legality, morality, and ethics if we are to remain a nation led by the rule of law.
Not if they are an American and not in the act of carrying out an assault or terrorist act. We do have rights in this country. If we allowed that who's to say who is a terrorist or not? They "could" say someone who protest or belongs to the Tea Party or the NAACP is one.