What protected American merchant ships in the Atlantic before the US entered World War 2?

Before the U.S. entered World War II, American merchant ships in the Atlantic were protected by the U.S. Navy's neutrality patrols, which aimed to safeguard American interests and vessels from submarine attacks, particularly from German U-boats. Additionally, the U.S. implemented convoy systems, where merchant ships traveled in groups, escorted by naval vessels to enhance their safety against potential threats. Despite these measures, tensions escalated, leading to increasing attacks on American ships, which contributed to the eventual U.S. entry into the war.