In 1915 a british passenger liner was sunk by German u-boats 128 americans died and many more people died germany kept attacking American ships. After this Britain intercepted a telegraph that was meant for mexico from germany telling them if they declared war on the United states they would give them Texas, New mexico, and Arizona after this the United states declared war on germany.
On April 21 1898 The spanish american war started, the spanish american war is the first war that america is involved in that isn't in the United states. The main reason of the war was to try and give cuba freedom from spain. The Americans win the war it ended on august 13th 1898.After the war there was a peace treaty and that was to give the United states Guam and puerto rico.
On june 28th 1914 the Archduke Franz Ferdinand was assassinated. There was a guy named Gavrilo Princip and he wanted to kill the archduke he already attempted to kill him but he messed but later that day he saw the archduke's car drive by and the driver took a wrong turn into the alley so he followed the car into the alley and shot him and his wife to death, this started would war 1.