Any hire car should be provided with an orange safety vest if it is a legal requirement. We hired a car on Madeira last week, and it came with a safety vest.
I may be wrong, but I understand that the problem with Americans needing to have an IDP in some countries is because US driving licences are issued by the individual states and not by the national government. There are international agreements on the format of licences, but the US federal government cannot impose the requirements of this agreement on the individual states.
I am an E.U. citizen, so although my licence is written in English, it has the same format as any other European licence and so can be understood by the authorities in other countries.