Final answer:
The U.S. was initially unprepared for war and lacked a strong navy due to its isolationist stance, geographical advantages minimizing the perceived need for a large military force, and the limited range of its naval ships. Adviser Alfred Thayer Mahan's suggestions led to improvements, such as the Naval Act of 1890, which modernized the Navy, but at the onset of WWI, the fleet was still smaller than those of European powers. The United States mitigated its initial unpreparedness by implementing convoy systems and bolstering the British fleets against German U-boats.
Step-by-step explanation:
The U.S. unpreparedness for war and the lack of a significant navy can be attributed to various reasons. Initially, America had maintained an isolationist approach through the 19th century. The geographical advantage of oceans on either side made the U.S. less prone to overseas conflicts, aligning with its diplomatic efforts to avoid foreign entanglements. Furthermore, the influential naval strategist Alfred Thayer Mahan recognized the limitations of the U.S. naval capabilities and stressed the need for a stronger navy, a network of naval bases, and a canal through Central America to aid in faster naval movements. The Naval Act of 1890 was significant in this regard, as it marked the beginning of modernizing the U.S. Navy, propelling it to third in global military rankings by the turn of the century. However, by the time the United States entered World War I in 1917, it still did not match the ship numbers of European powers. Effective measures such as utilizing the convoy system and increasing escorts for British fleets helped counteract German submarine warfare and consequently allowed the U.S. to bring substantial force to bear in Europe. Despite the initial unpreparedness, the U.S. managed to provide essential support, which played a crucial role in the later stages of the war.