It's the Zimmermann Telegraph. Basically, Germany was like, "Mexico, help us and we will give you your land that America took from you." Britain deciphered the telegram and then sent it along public lines to America. This way Germany would think that someone betrayed Germany. America received the telegram.
One of the main reasons the US entered World War I on the side of the allies was because the Germans had sunk the Lusitania, a passenger ship containing many Americans.
Canada
The United States entered the war for many reasons. The number one reason was that the Germans were sinking neutral ships, including U.S. ships and killing Americans.
The US entered World War 1 on April 6, 1917. The war ended about one and a half years later.
According to Historians, one of the reasons the U.S. entered World War I was to stop the spread of German Imperialism. Another reason was to spread democracy globally and strengthen allied support.
That's debatable because Germans used them a lot to prevent trade. Yet they are also 1 of the main reasons the United States entered the war. The United states entered the war because the Germans kept breaking the rules we set and didn't keep their promises with the submarine warfare. So the answer would be yes, they were one of the greatest impacts on World War 1.
The sinking of the Lusitania was a big one.
The Japanese attack of Pearl harbor
The allies had a huge number of supplies and arms on their side when they entered World War II. They also had air supremacy which was one of the major turning points in the war.
Stalin was dictator in Russia .
The US transported supplies to the Allies using merchant and passenger ships carrying United States citizens. This was why the German U-boats attacked these ships and were one of the reasons the US entered the war.
The United States entered World War I in 1917 because of several reasons. One of the main reasons was Germany's unrestricted submarine warfare, which threatened American lives and interests. Additionally, the interception of the Zimmermann Telegram, in which Germany proposed an alliance with Mexico against the US, further pushed the US towards joining the war on the side of the Allies.