This article analyzes why immigrant religion is viewed as a problematic area in Western Europe in contrast to the United States, where it is seen as facilitating the adaptation process. The difference, it is argued, is anchored in whether or not religion can play a major role for immigrants and the second generation as a bridge to inclusion in the new society. Three factors are critical: the religious backgrounds of immigrants in Western Europe and the United States; the religiosity of the native population; and historically rooted relations and arrangements between the state and religious groups. [ABSTRACT FROM AUTHOR]