The United States did use onslaughts of bombs. Prior to the atomic bombs, the United States firebombed at least 67 Japanese cities with raids of hundreds of B-29s.

This is a rather basic part of the history — I might suggest that you do a little more research before you conclude anything else (the atomic bombs did not "devastate the nation" and whether they were necessary or not should be a conclusion of your research and not the starting point).