I won't disagree with that. The New Left was only a small part of the population, and the division didn't run on party lines, in so far as many Democrats were, by today's standards, rather conservative on foreign and social policy. Since then leftist ideas have become more diffused in the population. But "diffused" in both senses of the word: more widespread, but also weaker and more diluted. We don't have that mass of conservative Democrats in the South and in White ethnic communities, but we don't have student radicals bombing and celebrating arson and mayhem. We are more equally divided at the polls, but less bitterly divided in attitudes.
And the liberal or leftist ideas that have been spread are social and cultural ones, while leftist economic programs have largely languished. What it amounts to is a chunk of the middle classes becoming influenced by swingers and leftist academics. But how large a chunk is it? And isn't it offset by academics and swingers becoming "bourgeoisified"? How much of today's political attitudes are simply poses and consumer choices, rather than programs of radical action?
The right wasn't anywhere near as radical as the left, but its ideas have also become "diffused" in both senses of the word. Dole, Bush, and Limbaugh are regarded as being more in the "center" than Goldwater or Wallace, either because conservative views changed or because conservatives moved the center to the right or because issues today don't inspire the kind of venom that they did thirty years ago. The right has become as "bourgeoisified" as the left.
I'm inclined to think that the political system has more or less worked. True, people argue with each other and call each other names, but that was true in the Jeffersonian and Jacksonian periods, the Progressive era and the New Deal, and the country survived. A generation ago conflicts over abortion, homosexuality, drugs and other social issues were something of a departure from the early bread-and-butter political issues (which caused quite bitter divisions at earlier times) and it was natural to think that culture wars might tear the country apart.
But we've been living with such divisions for a generation and the country's still here. It's entirely possible that a future election or court decision will put us at each other's throats again, but for the time being such conflicts are more or less "defused." Maybe I'm wrong, but it looks like when the dust clears we are still one country, some of us a little more of this, others a little more of that, but few of us purely one thing or the other. Politics still matters, but I don't see the apocalypse around the corner.