Hi,
You largely answered your own question.
"I find it curious that there aren't many symbols of a Catholic nature especially given Catholics' penchant for symbolism. But since we largely emulate American guns and America was largely protestant at the time, it would make sense."
Maryland had a significant practicing Catholic population but it was an exception. When the rebellious colonies tried to entice Canadians to join them in 1776, they sent John Carroll from Maryland along with Ben Franklin and others. Carroll was one of the few prominent practicing Catholics in the colonies and he was expected to appeal to the French Canadians. The Congregationalists in New England also likely would not use Catholic symbols despite their proximity to French Canada. You do find religious art dealing with saints, martyrs, and bible stories on European guns throughout the 1500s, 1600s, and 1700s. However, you also see pornography, either overt or couched in Greek mythological stories in about equal measure to religion.
dave