The us joined ww1 in the year of 1917.
1914
The u.s did join WW2
In 1890.
In 1787.
1861
The 8th of December 1941 was the date that the US joined world war 2
1845
Yu mean how* not who* & the us join the ww1 cause they wanted to become a world power & joinin world would defently help.
World War I
in 1956
in 1956