It really doesn't make any sense to have an IDP in an English-speaking country if your own DL is in English. Maybe the statement in the OP's opening missive really was aimed at non-European licenses from non-English speaking countries?

The only two Western European nations I know of that do require the IDP by law are Austria and Italy--though there might be others. I know for certain that France and Germany don't require one. (Unless they changed their laws in the last month or so.)

Rental car companies, even in Italy and Austria, don't normally ask for the IDP--they just want your money or plastic and to see your actual DL so can they have some degree of confidence that you know how to drive.

From what I've read here, I'm sure you could use your european A,T or L Class licence to drive in the USA :D Perfect!

I don't have a US license anymore and have had no trouble renting cars with my French license in the US -- I think that people would have to come from a very obscure country (Mongolia? Congo DR?) to have a national license refused by the major car rental companies these days.

Does anyone know if I need a IDP to rent a car in Scotland if I have a valid US driver's license and a valid Germany driver's license?

Believe it or not (and sometimes it's hard to tell) but they speak the same language in Scotland as we do in the US -- so the idea of having a translation of your driver's license to other languages really makes no sense. No it is totally not required.

Meanwhile, sharonmc, I'm curious why you topped this 20 month old post to ask your question that was already specifically answered by several people within it (unless you somehow thought that having a German license would in some way negate having a US one)?

Your (west) german license, no matter if it's the big grey one, the old pink or a card can be used all over the EU without the need for an IDP/IDL.

What about renting a car in Spain? Do I have to have an IDP for that?

Yes, Spain does require an IDP.