When travelling from Norway to the US, most flight companies allow you to bring two bags, each carrying 23kilos(50lbs) plus 8kg(17,5lbs) handluggage each. This might seem much, but one semester is a long time, and might require different gear and clothing. Instead of overpacking, which gives you a lot to drag on and costs a lot extra, try to think what you really need and what can be bought there.
Rolling suitcases might be best, as fully packed suitcases might be heavy to carry. A baggage-strap might be useful if your bags and suitcases are so full that they can burst open when handled by workers at the airport (personally, I can reccomend and ordered this one from the internet).
Folded jeans, shirts and sweaters can be placed together with heavy objects in the bottom of the suitcase. Light and small clothing can be placed on top, like socks and underwear. Consider which clothes and objects are the heaviest. Light clothing like a bading suit will not take too much space and weight, but objects like hairdryers and straighteners, are not that smart to bring as they can be bought cheaply in the US and be left there. Converters might be useful for the electrical things that you bring with you, but are not needed if you buy your electrical products in the US.
The things most valuable to you and the things that you will use during your travel should be kept in the hand luggage. Books, MP3-players and computers can be good to bring on the long flights. A little pillow can also be useful and make your trip feel shorter, as you will be fast asleep. Anyway, here is what my suitcases looked like: