myth, the us couldnt have use them to "obliterate" russia, the nukes then were small comparative, large and heavy, and the only way to drop them were by large bombers and the USA didnt have all that many of them and by 49 the ussr had their own.
The US had plenty of B-29s.:
Unlike many other WWII-era bombers, the B-29 remained in service long after the war ended, with a few even being employed as flying television transmitters for the Stratovision company. The type was finally retired in the early 1960s, with 3,960 aircraft in all built.
Boeing B-29 Superfortress - Wikipedia, the free encyclopedia
Just that not all of these could actually drop THE bomb:
Silverplate was the code reference for the United States Army Air Forces participation in the Manhattan Project during World War II. Originally the name for the aircraft modification project for the B-29 Superfortress to enable it to drop an atomic weapon, Silverplate eventually came to identify the training and operational aspects of the program as well.
Between February 1944 and December 1947 a total of 65 B-29s were modified to Silverplate specifications in five increments. Ultimately 53 of them served with the first nuclear weapons unit, the 509th Composite Group
Silverplate - Wikipedia, the free encyclopedia
Russian variant Tu-4 reverse engineered from regular not Silverplate B-29 had lesser range and payload:
The U.S. refused to supply the Soviet Union with B-29 heavy bombers under Lend Lease, despite repeated Soviet requests.[1] However, on three occasions during 1944, individual B-29s made emergency landings in Soviet territory after bombing raids on Japanese Manchuria and Japan. Stalin tasked Tupolev with cloning the Superfortress. The three B-29s were flown to Moscow and delivered into Tupolev OKB. One B-29 was fully dismantled, down to the smallest bolt, the second was used for flight tests and training, and the third one was left as a standard for cross-reference
The Tu-4 first flew on May 19th, 1947, piloted by test pilot Nikolai Rybko.[4] Serial production started immediately, and the type entered large-scale service in 1949. Eight hundred and forty-seven Tu-4s had been built when production ended in the Soviet Union in 1952.
The Soviet Union used the metric system, thus 1/16th inch (1.6 mm) thick sheet aluminum and proper rivet lengths were unavailable. The corresponding metric-gauge metal was thicker; as a result, the Tu-4 weighed about 3,100 lb (1,400 kg) more than the B-29, with a corresponding decrease in range and payload.
Tupolev Tu-4 - Wikipedia, the free encyclopedia
Even when they did manage a nuclear capable version, Tu-4A numbers were not very large either and they first appear 1952 (Korean War):
The deployment of the TU-4 bomber began in 1949, and they replaced wartime bombers such as the IL-4, B-25, PYE-8, B-17 and B-24 aircraft in Long-Range Aviation units. Patrolling mainly over Soviet territory, the bombers had a capability to strike at Europe, Northern Africa, the Near East and Japan.
Immediately after serial production of the Tu-4 was initiated, work began to adapt the bomber to strike at American territory. Some airplanes were outfitted to carry nuclear bombs and were designated as TU-4A. During re-equipment, the bomber was equipped with a thermostatically controlled heated bomb bay, a suspension unit for the bomb was developed, and biological protection devices for the crew were supplied. Some TU-4 bombers were equipped with aerial refueling devices, and very few were outfitted with additional fuel tanks located under the wings. They were deployed in 1952, though the majority of the TU-4 were not re-equipped with air refueling.
Although the limited range of the Tu-4 rendered it incapable of striking the United States and subsequently returning to bases in the Soviet Union, neither country was a stranger to one-way strategic bombardment missions, given the precedent of the FRANTIC operations in World War II.
Tu-4 BULL - Russian and Soviet Nuclear Forces
Kind of like a smart kamikaze bomb ....
By that time, that whole concept was getting outdated:
In 1953, the USSR initiated, under the direction of the reactive propulsion engineer Sergey Korolyov, a program to develop an ICBM. Korolyov had constructed the R-1, a copy of the V-2 based on some captured materials, but later developed his own distinct design. This rocket, the R-7, was successfully tested in August 1957 becoming the world's first ICBM and, on October 4, 1957, placed the first artificial satellite in space, Sputnik.
In the USA, competition between the U.S. armed services meant that each force developed its own ICBM program. The U.S. initiated ICBM research in 1946 with the MX-774. However, its funding was cancelled and only three partially successful launches in 1948, of an intermediate rocket, were ever conducted. In 1951, the U.S. began a new ICBM program called MX-774 and B-65 (later renamed Atlas). The U.S.' first successful ICBM, the 1.44-megaton Atlas D, was launched on July 29, 1959, almost two years after the Soviet R-7 flight.[2][3]
Military units with deployed ICBM would first be fielded in 1959, in both the Soviet Union and the United States.
http://en.wikipedia.org/wiki/Icbm
Plus you had newer nuclear capable bombers by then:
The Convair B-36 "Peacemaker"[N 1]was a strategic bomber built by Convair and operated solely by the United States Air Force (USAF) from 1949 to 1959. The B-36 was the largest mass-produced piston engine aircraft ever made. The B-36 was the first bomber capable of delivering any of the nuclear weapons in the US arsenal from inside its two bomb bays without aircraft modifications. With a range greater than 6,000 mi (9,700 km) and a maximum payload of 72,000 lb (33,000 kg), (and thereby having the ability to carry both the US's atomic fission and fusion weapons), the B-36 was the world's first manned bomber with an unrefueled intercontinental range. Number built 384
http://en.wikipedia.org/wiki/Convair_B-36
The B-47 entered service with the United States Air Force's Strategic Air Command (SAC) in 1951. It never saw combat as a bomber, but was a mainstay of SAC's bomber strength during the 1950s and early 1960s, and remained in use as a bomber until 1965. Number built 2,032
http://en.wikipedia.org/wiki/B-47_Stratojet
In the late 1940s the Soviet Union was strongly committed to matching the United States in strategic bombing capability. The Soviets' only long-range bomber at the time was Tupolev's Tu-4 'Bull', a reverse-engineered version of the American B-29 Superfortress. The development of the extremely powerful Mikulin AM-3 turbojet led to the possibility of a large, jet-powered bomber. The Tupolev design bureau began work on the Tu-88 ("Aircraft N") prototypes in 1950. The Tu-88 first flew on 27 April 1952. After winning a competition against the Ilyushin Il-46, it was approved for production in December 1952. The first production bombers entered service with Frontal Aviation in 1954, receiving the service designation Tu-16. It received the NATO reporting name 'Badger-A'.
http://en.wikipedia.org/wiki/Tupolev_Tu-16