Three years.
Otto Frank was NEVER in World War 2. He was a survivor from the Holocaust. Anne Frank's father.
The US did enter World War 1, though not till 1917.
The US entered the war in April of 1917 and were on the Allies side.
The Vietnam war
Three years.
Nothing specific, the US was fighting a war for most of the time during the Holocaust.
This question confuses the Holocaust (genocide) with World War 2.
It looks as if you are equating the Holocaust with World War 2. The two were distinct.
In effect the US did stop the Holocaust. By aiding the Allied victory, in defeating Germany, the Holocaust was stopped. If the US could have stopped it sooner, it is possible that they could have, but at great cost.
the US supplied much hardware for the allies to achieve a military victory over Germany and the Axis powers, thus ending the war and the Holocaust.
Otto Frank was NEVER in World War 2. He was a survivor from the Holocaust. Anne Frank's father.
The US fought in World War 2 from 1941-1945, but that is not the same thing as the Holocaust. Please see the related question.
During the Holocaust, there was a war going on and immigration to the US was basically halted.
Which war?
The US did enter World War 1, though not till 1917.
Africa