Final answer:
The factor that did not lead the United States to enter World War I was 'c. its long-standing alliance with Great Britain' as the US had no formal alliance with Great Britain requiring them to enter the war. Other factors like the Lusitania, unrestricted submarine warfare, and the Zimmermann Telegram directly affected US interests, prompting war entry.
Step-by-step explanation:
its long-standing alliance with great britain:
Its long-standing alliance with Great Britain. The United States did not have a formal alliance with Great Britain during World War I. The factors that led to the US entanglement in the war were largely connected to direct actions that affected American interests.
The sinking of the Lusitania was a significant event because it resulted in the loss of American lives and was a catalyst for changing public opinion toward the war. Germany's use of unrestricted submarine warfare was another key factor that violated neutral rights and threatened American commercial shipping. Lastly, the Zimmermann Telegram was seen as a direct provocation, suggesting a military alliance between Germany and Mexico against the United States, which steered public sentiment toward intervention.
In contrast, the claim of a long-standing alliance with Great Britain was not a deciding factor for entering the war. While the US had shared language and cultural ties with Great Britain and had provided support through trade and loans, this did not equate to a formal alliance obligating the US to join the war.