Being over the combined weight rating from the owner's manual has no legal ramifications, at least in most, if not all, states.
Your truck is registered for a certain weight.
Your trailer is registered for a certain weight.
In the odd event that an RV were pulled over and weighed by a DOT officer, those are the weights that would be used to determine if you are legally overweight.
However, DOT as a general rule does not waste its time with RVs, and a regular highway patrol officer would only pull an RV over if it were committing a moving violation, such as speeding.
Heck you can pretty much weigh whatever you want with an RV in the United States and it's perfectly "legal" as long as it's under 26,001lbs. Whether you can control it, whether you will like driving it, are whole different discussions.