Religious ties of recent immigrants are relatively low for Christian Protestants and more for all Christian denominations. The data is from 2003 but likely has been consistent since, if not more non-Christian. A 2015 update is here, which says that the percentage of unaffiliated has grown from 12% in 2003 to 20% in 2015.
“Immigrants are far less likely to be Christian than are Americans; and among those who are Christian, immigrants are far more likely to be Catholic or Orthodox than Protestant. Whereas 81% of adult Americans are Christian and 55% are Protestant, only 67% of new immigrants reported themselves to be Christian and just 17% were Protestant.
Whereas non-Christians together constitute only 4% of the U.S. population, they made up 20% of the 2003 cohort of new immigrants. Although Jews are represented at roughly the same level among Americans and new immigrants (1.4% and 1.3%, respectively), Muslims, Buddhists, and Hindus are substantially over-represented compared with the U.S. population. Muslims comprise 7% of new immigrants but just 0.6% of all Americans; and for Buddhists the respective figures are 4.3% for immigrants and 0.6% for Americans, whereas for Hindus the figures are 5.6% for immigrants and 0.4% for Americans.
Whereas 12% of immigrants said they had no religion, the figure was 15% for adult Americans. Thus today’s immigrants are slightly more likely to subscribe to a religious affiliation than most Americans, but the denominations they do affiliate with are quite different from the population generally.”
Some religions are largely driven by immigrants:
The 2015 figures from Pew Research show that 87% of Hindu adults living in the U.S. are first-generation immigrants, 61% of Muslims were born overseas. Among Christian traditions, Orthodox Christians have the greatest share of members born abroad — 40%.