Until relatively recently, both Europe and most of North America were considered the bulwark of Christianity,  No longer!  Non-Christians have become numerous not only through immigration as well as importation through slavery, but also through conversion, like right in the USA!  And the non-whites among them have posed quite the challenge to the white-supremacist types!  For their part, many Christians have been slow to unwilling to accept their brotherhood and sisterhood with non-Christians, or those Christians who march to the beat of a different drummer, or the "nones."  Perhaps that non-acceptance is a factor that makes Christianity less important, or even less than important.