Reading up on suburbanization in later part of 20th century, the general gist I get is that it happened because it provided a nicer home environment and the advent of cheap cars+highway infrastructure made it both desirable and practical.
Given the time period during the cold war, I'm wondering if there were any government policies partially driving this that had the goal of lessening the effects of any nuclear attack.
I've never found any evidence of this. Rapid suburbanization was already well under way in the 1920s—just interrupted for a few years by the Depression and war. A previous discussion of the subject.