However, from Germany to the US seems to take a bit longer, about a week/ week and a half.
I think you have that backwards.
In my experience going from germany to the US is quicker than vice versa.
Exactly. A letter to home takes 6-7 days and only 2 of those days are required for it to leave Munich and be on a plane out of Frankfurt heading to the states. When I lived in Md., it took a week to 10 days fro a letter to go to N. Virginia. A distance that I could have driven within an hour by the way.