Hello everyone!
I do not see a thread for mail from the United States to Prussia, so I thought I would add one here.
Here is an example of the 28 cent per 1/2 ounce rate from the United States to Prussia. This 1866 letter was carried on the HAPAG Line's Teutonia and was offloaded at Southampton and taken to Ostende, Belgium. The 7 cents passed to the Prussian mails covered the Prussian internal rate plus 2 cents for the Belgian rail transit from Ostende to Aachen.
Best,
Rob