Though it does not hurt to be safe, I would guess that, pragmatically, most people don't worry too much about the translation. I have a US drivers license and have never had to show anyone my international driving permit.

I've rented cars in a few EU countries including Germany, had to have a police report filed in Amsterdam for damage to a car, and been pulled over by German police (who were randomly looking for marijuana as I was driving from the Netherlands in the wee hours of the morning). All rental companies and police officers accepted my license as it was.