Actually, I can see the point for countries that have different alphabets (or non-alphabets, i.e, China).

Thanks all for your replies. They were all instructive, and I learned some new useful things I did not ask for as well.

I am heading down to my local AAA with photos in hand to get my IDP.

In addition to being a translation, the posession of an IDP demonstrates that you acquired the thing becuase you HAVE a valid license. The 50 US states produce 50 different drivers licenses; you can't expect a police officer in a European country to be able to look at a US license and tell whether it's a legit legal document -- or to even have ever heard of Ohio. Presenting the IDP shows that the accompanying license was documented as real by the issuing US agency.

BTilke - passports are easy to "figure out" since there are international standards for them, ie, all the items are numbered, and they all follow the same pattern, regardless of the issuing country. So item #1 is always the surname, #2 is the given name, #3 is the DOB (or something), and the list goes on. Most countries AFAIK conform to this standard so that international travel is made possible/easier. Similarly, the two lines of coded text for machines at the bottom of the picuture page all conform to an agreed upon standard.

Driver's licenses are another thing. US licenses are a lot more "colorful" than EU licenses - ie IMO they look "less serious". Nowhere on my US license does it say what kind of vehicle I'm allowed to operate (ie motorcycle vs car vs bus) - something that is required on a EU license, and something EU police may look for...