Cold War

The Cold War was a sustained, lengthy state of political and military unrest between national powers after World War II. It was termed as "cold" because there was no large-scale fighting directly between the major superpowers, although there were major regional wars, known as proxy wars. The Vietnam War was one of these proxy wars that saw both anti and pro communist forces battling for supremacy over their ideological principles. In the real world, the Cold War lasted from 1947-1991. The Soviet Union collapsed in 1991 and the United States and China were able to form friendly relations with one another after President Nixon's 1972 visit to the latter. Despite the war in Vietnam being present in both realities, it is unknown how accurate the Cold War was in the Fallout world.

The tensions ended sometime before 2052, albeit temporarily.

Influence on the Fallout world
As the Cold War never ended, the general mindset of the people still lean towards pragmatism and ruggedness, which has immense influence on the shape of the Fallout world.

Technology
The looming prospect of the Cold War halted almost all domestic demands for advancement of technology. The few exceptions are by-products from military development, such as robotics and medicine (e.g. Mr. House, protectrons, stimpaks, RadAway, and various performance-enhancing drugs). Other than that, technology mostly stayed stagnant from the 1960s.

Transportation
Land transport remained largely as it was as the culture never tuned into "sleekness" nor see the point of downsizing. As a result, most land transport had no further development beyond the 1960s. Due to the increasing cost of fuel, air and sea transport was drastically reduced close to nothing. This is evident with the few and sparse commercial/domestic aircraft and boats in both East and West Coast.

Military
The Cold War allowed military to develop with almost limitless restrictions, which explained the massive disparity between commercial and military technologies. An exception is the domestic robotics that can handle house chores and basic survivalist skills (e.g. Mr. Handy). Transport-wise, The USAF developed Vertibirds (seen throughout the games) and helicopters (as seen in Conrad in Fallout 4) for air travel. Advanced nuclear submarines were also developed.

Besides transport, the USAF developed Power armor, advanced exoskeletons that increased the operator's strength and resilience and could mount various plates to further increase its durability.

Pop Culture
As there were never diplomatic visits to China and Russia, the realization of potential economic development never happened. The people within the country were suspicious of foreigners. With that, communities were closed and there was no information about other countries in the US. Rock and roll, as well as other trends, never took place, explaining why the songs in the Fallout world predate 1961.