One of the more simple ways to tell is to familiarize yourself with what normal M-B door jamb ID plates look like. All US version cars since 1969 have a production date stamped on a small plate in the door jamb (Month/Year). Some of the Euro cars will have an ID plate added with the name of the importer(usually an individual) and a date on it....but the size and design of the plate are different. None of the European cars will have an "official" production date on the car.
There is also a difference in the ID tags on the radiator support. US cars have an emissions label(unless they have been in an accident and had the support replaced). European cars will have a black and silver ID plate on the radiator support with headlamp angle information.
Other differences include bumper and door reinforcement bars that had to be added to Euro cars for the required DOT conversion.
ASE Master Tech
Mercedes Tech 19 Years