Because they had many ways of doing things and were a very intelligent society.
-Hope it helps.
First event leading to US's enter into WWI:<span>Sinking of the Lusitania.
May 7, 1915.
American gov said stop unrestricted warfare.
Germans said okay.
</span>Second event leading to US's enter to WWI:<span>Germany publicly announces using unrestricted sub warfare again.
January 1917.
America gives second warning.
Germany ignores warning.
</span>Third event leading US's enter into WWI:<span>Zimmerman.
Telegram sent to mexico by germany.
Intercepted and decoded by great britain.
translation given to US in Feb. 1917
America begins to mobilize for war.
</span>Fourth event leading to US's entrance in WWI:<span>April 1917.
German U-boats sink four US merchant ships.
America enters the war April 6 1917.</span>
