Intl drivers license

Just about every state in the US has a different requirement for a driver's license. Some have no specifications saying what the license is. Some have no requirement for weights or whatever - other than CDL of professional drivers over 10,000. We have South Dakota licenses where there is no requirement for a special license to drive our 33,000 lb. Bus towing a 4,000 lb. car. Other states have weight requirements and some even require certification if you have air brakes. I read somewhere an estimate that about 40% of Mexican drivers do not have any license. I have no idea if Mexico has any special requirement for larger/heavier vehicles. I cannot speak about other countries further south. Our trick is to do nothing that would cause the police to pay attention to us so we will hopefully never have any need to show them a driver's license. So far in the almost 8 winters we have been driving this Bus in Mexico we have never been asked for a driver's license - other than at the border crossing where they just verify our identity and address etc. We have never had an International Driver's License and did not know there was such a thing.