It’s not just “secularism”—the absence of belief in God or absence of organized religion. Japan and China are extremely secular countries, more so than anywhere in Europe. The notable thing about the Netherlands seems to be not that they’re secular, but that they also were a hotbed of the Protestant reformation. Until the 20th century, the majority of the Dutch population was Calvinist. A few years after the Netherlands legalized same sex marriage—and long before most of the rest of Europe did so—Massachusetts became the first state to legalize same sex marriage. Massachusetts was founded by fundamentalist Calvinists (the Puritans). Even though American Calvinists and European Calvinists split (geographically) 300-400 years ago, their version of “secularism” evolved in a very similar direction, and quite differently than the “secularism” of Asian countries. It’s really hard to say that’s just a coincidence.