Answer: 1) Catholicism/Protestantism, 2) Slavery, 3) romanization, 4) influence of Arabian culture, 5) Africanization.
1) Northern Europe is Prostestant (different kinds of protestantism) since the 16th century whereas Southern Europe is Catholic (some parts are orthodox like Serbia or Greece, some parts are Muslim like Bosnia). This polarity does not exist in the USA (neither in the north nor in the south).
2) American South has a tradition of slavery which has still its reverberations today. It does not exist in European south.
3) southern Europe before being Christanized was Romanized which was very important for introduction of Middle Ages and Christianity later on. In northern Europe there was no Romanization, so Christianity was introduced to Pagan cultures. This contrast between the North and the South does not exist in the USA.
4) south of Europe was under influence of Arabian civilization (Iberian peninsula: both Spain and Portugal, the Balcans: Greece, Serbia, Bulgaria were Arabized for many centuries; south of Italy: Sicily at least) traces of which are still visible. It does not exist in the USA.
5) American south was partly Africanized because of the slavery during the 18th and 19th century. It does not exist in European south.