The allies did not bomb concentration camps during WW11. But do you realise that American Jewish leaders had some input into this decision. Concerns were held that bombing the camps could worsen the situation for the Jews held in the camps (remember that in those dark days, every day of life was held as a victory) and that such an action could be used by the Nazi's to alleviate responsability for the killing from them to the Allies. It may well have been better to have taken out the means of mass killing but it is wrong to suggest that the allies simply choose not to do so because they couldn't be bothered to help Jews. And yes, Israel is not helpless but neither is it all powerful. If Israel attacks Iran, then let it do so and reap all the consequences of its actions. Don't expect the USA to bail it out.
Israeli troops shoot, injure Palestinian crossing Gaza border fence (Haaretz)
from the article: Israel's plan to attack Iran put on hold until next year at the earliest