4 years.
The Holocaust was not the fault of the US! It is sometimes said that the US and their Allies did not do much (or anything) to stop the Holocaust. See the related question.
1945
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.
Not really. The US was in a different continent, so it was problematic. The decision was made that the best way to stop the Holocaust was to achieve a military victory against Germany, so all efforts were made to do just that.
Three years.
The holocaust says a couple things about ourselves today. Some people can act rash and harsh, and ruin the lives of others. This tells us that we will always have a few people out there who just cant stop doing the wrong things. But we cant let these few stop the rest of us. We can never forget the holocaust, so that we never make that mistake again. The world has come a long way since WWII. That has to show something about us. We learn from our mistakes and keep moving foreward.
100 miles if you don't stop probably less
One cannot say seventy years later what should have happened: The US did what it could at the time.
They talk about the holocaust?
Tried to persuade the germans to free some jews in exchange of weaponary
The US Army liberated some concentration camps, but many Jews slated for death had already been killed. Both the US government and the Vatican were blocked by German violations of the Geneva Convention, and the US had no means to stop the Holocaust other than to use military force to defeat the Third Reich.
The time it takes depends on us. The appropriate level can be reached if we stop CFC's.