Complex sentence: American war aims were to detach the war from nationalistic disputes or ambitions, after the Bolshevik disclosure of secret treaties between the Allies, which discredited their claims that Germany was the sole power with aggressive ambitions.
Split into simpler sentences: American war aims were to detach the war from nationalistic disputes or ambitions. The Bolshevik disclosure of secret treaties made between the Allies, had discredited their claims that Germany was the sole power with aggressive ambitions.