Only on test sites.
Bikini Atoll in the Marshal island chain .
All the facilities used by the US to prepare the materials for nuclear weapons, build nuclear weapons, design and test new nuclear weapons. This is all lead by the Department Of Energy.
The last U.S. above-ground (atmospheric) test was in 1963. The last U.S. underground test was in 1992. The Comprehensive Test Ban Treaty (signed by many major powers) ended testeing of all kinds, atmospheric or underground, in 1992. The U.S. models (with supercomputers) characteristics of nuclear weapons 'explosions' in order to 'test' its weapons designs.
The US signed the Comprehensive Nuclear-Test-Ban Treaty in 1996 which prohibits nuclear testing. Additionally, advancements in technology allow for testing through simulations and monitoring. The US also aims to set an example for other countries to follow suit in reducing nuclear proliferation.
The difference was that the US could test and improve it's weapons/equipment; the Soviets couldn't. But they could observe. Translation: Secret weapons weren't secret no more.
Most US weapons of any kind are made in the US.
The atoll used by the US for nuclear weapons testing is called Bikini Atoll, located in the Marshall Islands in the Pacific Ocean. The infamous Castle Bravo test, the largest nuclear weapon ever detonated by the US, took place there in 1954.
Both the US and USSR had deliverable nuclear weapons in the 10+ megaton range by 1955.
The UK was the third country to obtain nuclear weapons, after the US and the USSR. The UK had its first successful nuclear weapon test in October 1952, a plutonium warhead similar to the one dropped on Nagasaki.
US weren't effected by the Nuclear Weapons, They created it.
Soldier, test fire your weapons now!