If your flights are on one ticket, United thinks you can easily make it, so don't worry - after all it is their problem to get you connected, and if you miss your connection, they have to pay for your hotel, transporatation, and food in EWR.
From experience, the international flight will also wait for some connections if they are late.
Rebooking your connection to the next day is not a good plan - you will for sure 'miss' your connection on the same day, you will pay extra for the change, and you pay yourself for staying a night near EWR. Why pay United money to be allowed to pay for your overnight stay? Let them pay for it, if you miss the connection.
If making the connection is important for you (because you don't want to be a day late at the destination), you can call them and ask to get an earlier connection to EWR, there are several daily flights from CLT to EWR.
If you booked it on separate tickets (which I doubt), you should definitely move the first leg earlier, as you and your luggage will never make it - you'd have to go outside of security, and they wouldn't even accept your luggage anymore.