I think I understand. You have a ticket from Shanghai to Charlotte. Your first entry in the US is Chicago. You want to throw away the Chicago to Charlotte flight and fly on another ticket Chicago to RDU.

This is called "throw away ticketing". You want to only fly a part of your original itinerary. It is usually against the rules in the ticket you bought. In your case, you can probably get away with it because it is the last flight on your ticket.

There will be some things to know.

You clear customs and immigration in Chicago. You will have to get baggage then. If you were continuing on the original ticket you would then go to the transfer desk and give your luggage back to continue on without any additional fees. You would then transfer, usually staying in a secure area, to the gate for your flight to Charlotte.

Since you are not traveling on your original ticket you will now have to go out of the secure area and check in for the flight to RDU. You will need to check bags and pay any additional fees. You will then have to go back through security and on to the new flight.

This is the most likely scenario.

Make sure and give yourself plenty of time in Chicago.

Many say do not put in any frequent flyer numbers so the airline cannot easily track what you have done.

Try and make the new flight from Chicago to RDU on a different airline than your flight from China.