The answer is it depends on the home state (e.g. the state that issued the Drivers License). There are some states such as Texas that require a Commercial Drivers License (CDL) to tow a vehicle with a combined weight of 26,000 lbs or over. Some states also have length restrictions that put a vehicle into a commercial category. However, there are many states including Florida and Illinois where we are from that exempt Recreational Vehicles from commercial drivers licensing requirements.
Federal Law requires all states to honor licensed drivers from other states. What this means is that if you are licensed in a state that does not require a CDL license then you can legally drive through a state that does. Under my Illinois drivers license I can tow this huge rig through Texas legally while someone who lives or is domiciled in Texas would need a CDL to do the same. Of course that does not except us from the traffic laws in the state. We cannot carry more weight than our truck is rated for, we may not be able to go into a tunnel with propane on board, we may have to follow a truck speed limit, etc. It is always good idea to research the laws of the states you will be traveling through to make sure you are aware of what is legal and what isn't. If in doubt call and ask. The state police is a good source to call.