The high percentage of nonbelievers in Europe isn't exactly the same thing as anti-clericalism. There was a sharp decline in the influence of Christianity in most of Europe in the postwar decades; anti-clericalism, in contrast, was common among liberal and socialist intellectuals going back to the 18c, while France became an officially secular state in 1903 or so. This rise in social secularism happened in other modern or modernizing countries, though not the US: high-income East Asia, the core communist countries, China, parts of Latin America (e.g. Uruguay), Turkey. It's entirely possible that given its GDP trajectory Iran would've ended in the same place if Khomeini hadn't taken over in the Revolution. It's even entirely possible Iran is already in that place and nobody openly admits it.