As Paul points out, He expects His people to hold themselves apart from their neighbors and to avoid the worship of idols including he idol of the nation. God's demands are great. The obedience of faith is not something we can embark on lightly. As Christians we are judged by a higher law that ought to cause us to see our world in terms of a higher law. God is above the nation and the history of Europe provides numerous examples of why Christians need to remember this and cling to God's Word.
Culture is a strange thing.
Many of us are Americans, Brits, Canadians, French, German, Italian or simply devoted football fans before we are Christians. That's not good enough. God calls us to renounce all allegiances other than our commitment to Him. Once again eighteenth century Deists like Jefferson and Paine thought that this was an obscene thought and evil teaching. The history of Europe teaches otherwise because when men and women give themselves to forces or ideologies other than the service of God disaster follows.