TSA-approved locks for securing your luggage have the advantage that they can be used anywhere in the world. There are many variations of them - with code, with keycard and with keys. TSA is a system that allows luggage inspectors at airports in the USA to open and relock the locks without cutting or breaking them.
If you have locked your luggage with an ordinary lock when traveling to the USA you might risk having it cut or broken. There is not much to do about it afterwards because those are the rules there. Therefore, if you are planning a trip to the United States you should look into buying TSA-approved locks for your suitcases and bags.