Socialism got decimated in America after the 40s because of the backlash against the New Deal. It got hit even harder by Reagan's neoliberalism which eliminated working class interests or at least misguided them to corporate interests.

The propaganda against left wing movements (anarchism, socialism, Marxism, etc) kept them out of politics and concentrated efforts into the neoclassical economic viewpoints. From left to right is liberalism, libertarianism, and conservatism. Those are the main three neoclassical views that got a lot of notice and concentration while socialism was pushed out on a number of levels. Academically, it wasn't taught. Based on who owns corporations, it wasn't told what class struggle means except a liberal view that says rich versus poor. That's certainly one notion of class, but it doesn't get to the heart of the issue.

For Socialists, they've been conflated with liberals through social democracies which aren't exactly Socialist countries. They're a step in the right direction, but everyone is fighting for different permutations just as other neoclassicals fight for the One True Capitalism.

Getting back on topic, liberals and conservatives have had a monopoly on political economy for the last 100 years. The ways that SJWs have come up is through the 40 year hussle known as capitalism. It's not a coincidence that SJWs are mainly trust fund babies. They are the recipients of wealth earned by the working class and concentrated into the rich. You look at Anita Sarkeesian, Mcintosh, Lipshitz, Quinn, and any others and you'll see that they have a wealth privilege in being able to live in San Francisco, which is pushing out poor minorities while being one of the wealthiest areas on the planet.

Now think about what occurs as you have wealth... You spend less money, you have few connections to the majority of people and the things you focus on are vastly outside the norm. You don't have that connection to others when the few people you know are just as rich as you are and the community you come from is very sparse. Liberalism is still upper middle class interests and fits that description far more than Socialist or the whole "Cultural Marxist" misnomer that right wingers use to smear everyone that isn't them. I could go on, but this is long enough to give you a sense that American politics are FUBAR and unfucking it takes far more education than some people are willing to give.