What prompted president Wilson to bring united stated into world war 1?

Answer 1

President Wilson was prompted to lead the United States into World War I by several factors. The most important was the unrestricted submarine campaign announced and then enacted by Germany, which led to the loss of American lives and goods. Also involved was a more general pro-war and anti-Germany sentiment that had increased among Americans.
The US were not happy with Germany due to the policy of unrestricted submarine warfare that they were emplying on ships heading to Britain which was causing the deaths of many American civilians. However this alone was not enough to turn public opinion completely against Germany as Britain was blockading the German coast aswell (but not as violently).

But when the US government discovered that the Germans were brokering an alliance with the Mexicans, offering to assist them in claiming back territory it had previously lost to the US, that was the decisive tipping point for the American public who began to call for war.