History, Politics and International Relations majors here.
Unbiased opinion: The world is just like a particularly nasty neighborhood. You have the thieves, the thugs, the wimps, the idealists/dogooders, the cops, and the people that are just trying to get along. Occasionally gang warfare breaks out, the cops get corrupt, the crims go straight, and whatnot. Just think of countries the same way you think of people, and that will clear up your point of view. Countries are just made up of people, right? Then why should they act any differently?
Don't buy the post-modern, constructivist BS that they try to feed you. Take what they teach you, compare it to the real world, and ask yourself "does this theory match what I observe?" If the answer is "No", then take what you can from it and chuck the rest. They will try and tell you that you can't observe the real world, because your upbringing, beliefs etc bias you, so you cant really be sure of anything. Whilst there are grains of truth to this, it is mostly BS designed to eliminate unpleasant realities that interupt good theories.
The most important thing: Do your own reading, from your own sources, as well as theirs, listen to what they have to say, THINK HARD about it all, and come to your own conclusions. Just because a person has letters after their name doesnt mean that they are smart
rant off