World-wide the situation is far, far worse. In case you haven't yet noticed, most of the world still isn't Christian, and every other faith wants some variation of killing gays ... some faiths want them killed on sight even. The number of people wanting that is not really known, but reasonably, it's somewhere between 4 and 5 billion.
Liberalism is self-interest of middle class and upper-middle class people. But as you say, those social classes are disappearing, and not just because they don't seem to be having any kids.
The sad truth is, unless something fundamentally changes, the end of liberalism won't need to wait until the next generation, because those classes are being eliminated. You could say that it's economic policy, but that's not really true. I'd say technology and improved large-scale efficiency is mostly responsible. And that's inside America and Europe, in the rest of the world nothing remotely resembling liberalism stands a snowball's chance in hell of getting 10% of the votes.
Then there's general "environmentalism" and NIMBY/BANANAism that broken the compact between the city and countryside in California in the '70s, canceling the water projects necessary to keep up with the population growth of the former. Per farmer and intellectual Victor Davis Hanson, this year that's going to kill half a trillion dollars worth of agriculture, as an inevitable string of droughts require sending all the water to the cities.
Or the precipitous shutdown of the US coal industry; yeah, the stuff is extremely nasty and pretty much anything but bogus renewables (that can't scale, nor meet any demand cycle without even more expensive storage) would be better, but the speed and way this is being done is evil. And disproportionately hits fly-over country.
Or look at the XL pipeline, or unrestricted illegal, and way too great legal immigration. Etc. etc. etc.
All these are destroying working class jobs and lives, and the middle class ones that are based on them.
Take a few moments, if you can, and put yourselves in the mind of a conservative american. Consider what things look like to a conservative christian in favor of small government, living in a town whose industrial base has been nuked and who is now living through a construction bust, with no obvious "next thing" in sight, except perhaps uprooting their families to the Dakotas for oil jobs.
If we don't make room for them, there will, eventually, be war.