The American Civil War began as soon as President Lincoln was elected. Several states automatically withdrew from the Union and the first conflict began, when Fort Sumter was attacked. The Union was not equally wrong to the South, their whole desire was not to fight, but to UPHOLD the Union.
If the Americans decided to let Hitler have his way, millions more on top of those who had already been massacred would be dead. The European Jew Population would be non-existent. Tell me, how our interference in the war to end genocide, and to prevent the unwarranted indefinite takeover of several European countries by Nazi Germany was a bad thing?