In the United States, every religion under the sun, Christian and non-Christian, has a foothold, and no nation on Earth with a comparable level of economic development is so religious in practice. Religion is a fill in the blank question. No multiple choice option is comprehensive enough to fit a simple survey accurately.
In most of Europe, in any given place, there tend to be three predominant religious identifications. One is the established or formerly established form of Christianity -- Anglicans in England, Lutherans in Scandinavia and Northern Germany, Catholics in France, Spain, Italy and Southern Germany. A second, increasingly the second most common faith in most regions of Europe, is Islam. A third is some form of secular, atheistic or non-religious identification.
For example, in France, in a 2003 poll, religious self-identification was "62% . . . Roman Catholic, 7% Muslim, 2% Protestant, 1% Jewish, 2% "other religions" (except for Orthodox or Buddhist, which were negligible), 26% 'no religion'" Moreover, a significant share of those who self-identify as Catholic or Muslim see this as a cultural designation rather than a theological one and simultaneously view themselves as atheist, agnostic or believers in a far more vague form of divinity than Catholic or Islamic doctrine describe (about 12% of the French come from Islamic countries, and historically, almost all of the French were considered Catholics).
In much of what we think of as the Islamic world, almost everyone is considered Muslim and the only real alternative, as a default, is a secular stance.
Globalization could play out a couple of ways. One would be for secularism to arise as a consensus alternative in a world where most societies are multiple choice or either-or in their universe of culturally acceptable religious roles.
The other would be for the exposure to multiple world religions to turn what had previously been multiple choice societies from a religious perspective into fill in the blank societies as more options appear. For example, this appears to be happening in London.
Time will tell which response predominates.