Earlier quoted context omitted.
They know already. A perennial topic of annoyance for US immigrants in Sweden is that their US licence is only valid for a year here, then they have to retake their test (unlike immigrants from the EU who get to convert theirs automatically).
Germany restricts US driving licences depending on issuing US state. Denmark is apparently far more willing to let it slide, and anyone with a US driving licence can get it converted to a Danish one with just a doctor's approval. Although, in Denmark, their US licence is only valid for a month. But you don't have to retake the test. I am frankly a bit puzzled by this decision.
I always wonder about the situations that inspired regulations like these and exactly how they believe they're solving whatever that problem was.
Was there a rash of accidents involving drivers from Texas? Did someone from Delaware blow the German test so badly that they soured the state's reputation forever? Is this somehow American Top Gear's fault?