I was going to post further thought on political fashionableness, but got fascinated by Steve Sailer's new string of posts on "What caused the 60's?" It's a fun parlour game, and anyone can play, of course, because so many plausible theories can be brought forward.
Here's the catch: a commenter mentions that these events of the 60's had their parallels in many other nations. Thus, most of our explanations that point to American events of the 50's and early 60's - McCarthyism, Vietnam, GI Bill, whatever - could not have caused the cultural changes in Germany, Mexico, Japan, France.
My two pet theories - a younger generation with disposable income and color photography - hold up pretty well under that examination. They are not significantly strengthened, perhaps, but they remain standing while other theories crash and burn. Disposable income is relative to economies, and even if the amounts aren't much (Mexico City,) they matter if the purchasing power is a significant fraction compared to the parents' generation.
There is a further parallel with the Great Depression. Americans tend to speak of that even as if it were ours alone, and identify causes that are entirely internal: Smoot-Hawley, unrestrained speculation, shutting off immigration. But those things had little effect on other countries, which point to their own internal events as the cause of their respective Great Depressions.
I've know that both of these phenomena were global, but I keep forgetting it. What was your pet theory, and how well did it hold up to your plotting it against international events?