This study reviews and evaluates the intertwined relationship between immigration and religiosity, focusing on the two sides of the Atlantic – Europe and the United States. Based on the existing literature and on a statistical analysis of several data sets (the International Social Survey Program – ISSP: Module Religion, 2008; the European Social Survey – ESS, waves 2002-2010; and the General Social Survey – GSS, waves 2002-2010) the following aspects are explored: (i) the current religious landscape of Europe and of the United States and projections for the future; (ii) religiosity of immigrants (in Europe and the United States): are they more religious than the native populations (in terms of church attendance and of prayer habits)?; (iii) how does religiosity of immigrants affect integration: is it serving as a bridge that smoothens integration into the local population, or as a buffer against the harsh integration process?; and (iv) are the intersections between religiosity and integration different in Europe and in the United States, due to historical differences in the state-religion relationship, immigration policies and concepts? The main findings are the following: (a) immigrants are indeed more religious than the populations in the receiving countries. This fact, combined with higher fertility rates and also a continued inflow of immigrants, will lead to major changes in the religious landscape, both in Europe and in the United States; and (b) while in the united States religiosity of immigrants serves as a bridge between the immigrants and the local population, in Europe it has mainly the function of a buffer and of "balm to the soul".