Does anyone know how many of these rare cars made it to the US soil?

None were ever imported as new, since they didn't meet the North American
safety and emission standards. Mercedes had no problem selling the 502
units produced to buyers in Europe and Asia. Subsequently, a handful have
found their way into Canada and the US, perhaps less than 3. Word is that
the one in western Canada suffered from a rear end accident. Former DTM
versions, not to be confused with the 502 road cars, have been brought in
through Florida.