Yes, probably need more HP.
It's just that on the autobahn, some people can literally be driving so much faster, the differential can be quite substantial. In USA, the max differential between someone driving too slow to someone speeding is only around 50 KPH. Someone driving slowly is driving around 90KPH and someone speeding to the point the police will stop them is around 140KPH. So basically, as long as a car can comfortably accelerate from 100KPH to 150KPH is sufficient in the USA. And generally all powerful cars can do that.
But as you know, in Europe, that differential can be greater and is at the much higher end. So I'm realizing that I can't assume things work in Germany just because they work in USA conditions.