From what I have read, it only took one day for Germany to occupy Denmark. The reasons why is because it isn't very large, not in a very good defensive position, and it largely disarmed it's army...
This is going to depend on where you are starting from in Germany and going to in Tennessee.
An example:
Frankfurt (FRA) to Nashville, TN (BNA)
Shortest Flight Duration * 12 hours 11 mins *...