A Pew research showed that Greeks were the people that considered their religious faith an integral part of their national identity. To the question “Being a Christian is very important for being truly a (country/nationality)”, 54% Greeks responded that their religion was tied to their country/nationality, with the Poles coming a distant second with 34%. Americans (32%), Italians (30%) and Hungarians (29%) made up the top 5 countries.  Across the 13 countries where the question was asked, a median of just 15% say it is very important to be Christian in order to be a true national. Only in Greece do more than half (54%) hold this view, while in Sweden fewer than one-in-ten (7%) make a strong connection between nationality and Christianity. Generations are divided on this question, with those 50 and older placing far greater importance on being a Christian (44% say it is very important) than Americans under 35 (18%).
Men and women slightly differ on religion’s importance in American identity. More than a third (36%) of women say it is very important for a person to be a Christian; roughly a quarter (27%) of men concur.
Views on Christianity and nationality also differ along educational lines. People with a high school education or less (44%) are more than twice as likely as people with at least a college degree (19%) to voice the view that it is very important that one is Christian in order to be American.
Views of the importance of religion to nationality often divide along generational lines. People ages 50 and older are significantly more likely than those ages 18 to 34 to say that being Christian is very important to national identity. This generation gap is largest in Greece: 65% of older Greeks say it is very important but only 39% of younger Greeks agree. The differential is 18 percentage points in the UK, 16 points in Germany and 15 points in Hungary.
People on the right of the ideological spectrum are more likely to view religion as very important to nationality. This right-left divide is particularly prominent in Greece (26 points) and Poland (21 points). The ideological left is quite secular in Germany (just 5% say religion is very important to nationality) and Spain (6%). By comparison, a greater share of people on the left in Greece (40%), Hungary (26%), Italy (24%) and Poland (21%) say being Christian is very important to be truly Greek, Hungarian, Italian or Polish.

source: pew research