So events like the 60s civil rights movements and peace movements never occurred; they would occur sometime. People tend to forget that the 20's were full of radically liberal people and a society that started going crazy constructing new ideals and whatnot, and the Fallout's divergence of the timeline occurs after WWII. Given this, social revolutions would be popping up everywhere if not in the 60s, then in the 70s or 80s, or 90s and so on. I mean human beings in the 20th century do not just magically change so that they reflect the same xenophobic, communist-hatin' bigots for more than a century.
We've reached a stage in humanity where new fads and new ideals are popping up every decade, so how on Earth would the same fads, the same music, and remarkably primitive technology be around 120 years after the 50's? Ok, so I can see technology-wise how things diverged. Internet was not created and instead the basic type of Arpanet (?) (sorry I svck at this technical stuff don't know if I'm describing it right) stuck around. Fusion technology exploded (no pun intended) and new types of weapons evolved as it was a (cold) warrior based world where technological advances were focused on military advances.
Still, regarding society, how does one still remain stuck in the past after more than a century? Although energy weapons and robots would not be around in the game it would have made much more sense for the developers to simply have the nuclear holocaust occur in the 60s if they wanted a 50s type society by the 22nd and 23rd centuries.
end rant, like I said this has probably been discussed countless times before...