You people want quotes? Here you go. The plain truth is the United States was KEY to Allied victory in WW1, and there was no path to victory for the Allies
without the US' involvement in 1917.
Preface: Article 1534 of the US Navy Regulations of 1913 required formal permission from the Department of the Navy for publications such as
The Victory At Sea. Permission was formally granted by Secretary of the Navy Josephus Daniels to ADM Sims on 26 June 1919 (Appendix 1, p. 371; includes the text of Article 1534, Navy Regs).
Sims was then serving as President of the Naval War College, the US Navy's premier postgraduate school for warfighting at sea. Sims' book can reasonably therefore be considered an official, approved opinion of the United States Government.
In 1917, it (the RN) did not possess destroyers enough to both guard the main fighting fleet and protect its commerce from submarines
Page 36.
I (Sims) do not think the number (of British destroyers) engaged (in escort duty) ever exceeded fifteen.
Page 40.
Briefly stated, I consider that at the present moment (April 1917) we are losing the war.
Page 43.
By 5 July 1917, 34 US Destroyers were deployed at Queenstown. Additionally the destroyer tender Melville was deployed. Page 76.
Appendices 8 and 9 (pp. 400-401) show the success of the German U-Boat campaign and concurrent failure of Allied shipbuilders to make good on U-Boat losses. I would reproduce the chart, however the full original book is available on Google Books. I have an identical reprint from the mid 1980s, published by the Naval Institute Press.
In brief:
1) The Allies had insufficient ships to adequately protect shipping in the Spring of 1917 and were therefore losing the war at sea through the successful German U-Boat campaign.
2) Escort duty was almost exclusively an American show; ADM Sims was the first officer in the history of the RN to be placed in command of British sailors as Senior Officer Present Afloat at Queenstown (82).
Conclusions:
Without the US Navy, the Allies would lose the war by late Summer 1917. Russia was in chaos, nearly a million casualties had broken the French and the British would be unable to continue without a merchant marine; the German High Command could do math.
WITH the USN and the AEF, it is very difficult to see any plausible scenario prolonging the war past the fall of 1918. Again, the Germans could do math and the virtually bottomless pool of manpower provided by a nation of somewhere in the neighborhood of 100 Million souls that proved they could and would fight at Cantigny, the Belleau Wood and the Argonne was an insurmountable strategic and tactical advantage for the Allied and Associated Powers.