Europe is abandoning Christianity.

[Neo-Scholastic]

Secular means to not favor any particular sect, i.e. religious tests for office and no state sponsored church. It does not mean non-religious.

Google the Treaty of Tripoli, Article 11 sometime.

Often cited and often misapplied. All it implies is that there is no official state religion. It does not say that the USA is as a nation, people, or government must be free of religion, its expression, historical recognition, or hertitage. The USA is founded on universal principles of human dignity and liberty generally grounded in theism without partiality to any sect, including Islam.