German Lutherans initally immigrated to Philadelphia at the invitation of William Penn in the late 1600s, and made Pennsylvania the most German of the original 13 colonies.
Post Amercian Revolution, German (and Polish) Catholic immigrants played a major role in colonizing the rugged lands of the early American frontier in Pennsylvania. The rural German Catholic population became organized and established the nation's first Benedictine monastery, St. Vincent Abbey, in Latrobe, and the first Benedictine convent, St. Joseph Monastery in Marienstadt (St. Mary's), the town itself founded by the German Catholic Brotherhood. They also founded the surrounding Benzinger Township. St. Mary's/Benzinger Twp was one of the first fully German settlements in America.
German Catholics didn't just build churches in rural Pennsylvania, they built Catholic institutional complexes that dominated the culture of the countryside and exist to this day. That is why the novelty of a "land of cross-tipped churches" and the notion that Catholics are typically rare in rural areas are completely foreign to me.