When I immigrated to the United States by China Southern Airlines, did the 5 kg carry-on bag include clothes or something in my pants pocket? Are you strict with carry-on luggage now?

5 kg carry-on luggage is not strict, as long as it is not an obvious big bag, there will be no problem. In addition, it is best to put less things in your pockets and take them out one by one during the security check. Too many things in your pocket will make people feel abnormal and increase your examination. Therefore, if you don't need anything on the plane, you'd better put it in the checked baggage.