There was a very elaborate infrastructure in place- rail lines, train stations, gas chambers, crematoriums, and even the factories that made Zyklon B, that all came together for death camps to work.
Now if these structures are taken away, it is true that the Germans could resort to the old ways of execution. But that has its 'advantages'- Jewish uprisings, soldiers refusing, transportation problems, etc. This leads to a less efficient way of killing. Plus many German officers were worried about disposing of the bodies. They did not want any evidence left behind.
But it might not have been worth the effort (like others have said). Flying thousands of miles over enemy territory to bomb a target that does not directly effect the German war machine could be a deadly mistake for the USAAC. But I do think it would have saved some lives.