Since a lot of the robo calls are part of scams and illegal, I don't think it's the fear of fines. I believe that market size and language barrier are a bigger issue: Plenty of people speak english, few speak german and even fewer are fluent enough in swedish to convince people to hand over their money.
Might be a difference in the phone systems. Not sure if this is true anymore, but I've heard US caller IDs are easy to spoof, while it is basically impossible in Germany.
Also our regulatory bodies are most certainly stronger in this regard than the FCC.
