Why was the creation of the atomic bomb important?

It ended WWII 6 months sooner than it would have without it; saving thousands of American and Japanese lives by eliminating the necessity for an invasion of Japan.

Then, after the Soviets stole the plans for the bomb, the doctrine of Mutual Assured Destruction (MAD) characterized 50 years of the Cold War.

Today we face proliferation of nuclear weapons - small countries and even terrorist groups can credibly threaten massive destruction to even the largest opponents.

It opened an entirely new kind of warfare. Had the bomb never been invented, the Cold War would have been drastically different, perhaps avoided.

On the bright side, it prompted the global community to demand arms control, though perhaps unsuccessfully.

It is also a prime example of quantum mechanics and the application of theoretical physics.

well we won WWII we proved to the soviets that we were technologically superior to them, and we solidified ourselves as a world superpower.