Considering the potential loss of life to America and the actual loss of life to the Japanese (between 150,000 - 246,000 civilians), was Truman right to drop the bomb on Japan?

No it wasn’t right because USA was the one who created League of nation but itself didn’t became part of it. Although they knew the bomb would lead in devastation they threw bomb on Japan due to which the place where America threw bomb is still desertification where not a single plant has been able to grow.