From what I could find out, there was a failed plan (Operation Pastorius) that identified two targets of interest for sabotage in Altoona, PA: The Horseshoe Curve, and the PA Railroad's repair shops near Altoona, PA.
Did Nazi Germany learn of these targets through Nazi sympathizers in Altoona?
If they didn't acquire intel that way, how would they have learned about the tactical significance of these areas? The population of the area wasn't large at the time (80k?) and I can't imagine someone from another country having interest in a place like Altoona without some sort of prompt from someone else. It also contained a notable German population at the time - which prompts the question I raised in the title.
There is no mention of Nazi sympathizers in Altoona PA during World War II in the book "Operation Pastorius: Eight Nazi Spies Against America" by George Dasch. The Germans landed two separate groups in the United States in June 1942. Both groups had four agents that graduated from a Nazi sabotage school. The instructor for the railroad portion of this course was Reinhold Barth. Barth was born in Stuttgart Germany, but lived in the United States between 1929 and 1938. Barth was a draftsman for the Long Island Railroad. When he was laid off, he returned to Germany. He identified three main targets; Horseshoe Curve, the Hells Gate Bridge and the elevated tracks at Pennsylvania Station, in Newark New Jersey. All three were critical choke points on the Pennsylvania Railroad. The Pennsylvania Railroad proclaimed itself to be "The Standard Railroad of the World" and was very proud of its magnificent infrastructure. Reinhold Barth would not have had to work very hard to gather intelligence about the Pennsylvania Railroad. There was an article about "The Standard Railroad of the World" in nearly every issue of all of the railroad industry trade magazines, every month.