New Delhi, July 2 -- Growing up as a Christian, I often heard from other churchgoers how fortunate we were to live in a Christian nation such as the US. These days, I am more likely to hear fellow Christians lament that the country has fallen into secularism.

But as America turns 250, it is worth remembering that the history of Christianity in the country is complicated. So, too, is its future. Church membership has waxed and waned in the country before.

But the decline in a broadly shared Christian worldview is unprecedented. Already, it is putting the pluralistic religious ideals of the country's founders to the test.

The pre-1776 colonial era was a largely unchurched one. Church membership levels hovered around 15-20% due to strict ...