Civic nationalism is a form of Nationalism that aims to accept all current residents of a nation whatever their race, religion or language. Many, though not all, civic nationalists are liberal. A civic nation is one with free and fair elections, a government that reflects the will of the people, active citizenship, freedom of peaceful assembly, equal opportunity for all, freedom of the press and support for social programs. Differences in language, ethnicity, culture, and religion do not matter.
The USA is an example of a country badly split between civic nationalists on the one side, with religious and Ethno Nationalists on the other side. The Democrats and Moderate Republicans support a nationalism that includes all Americans while Ann Coulter and her type are uncomfortable about the idea that Americans can be Muslims, Atheists, Gays etc etc.
Nationalist movements can change their political ideology over generations and change which groups they accept or reject. The Irish Tricolour contains both Roman Catholic Green and Protestant Orange to symbolise the Civic nationalism of Wolf Tone and Charles Stewart Parnell, both of whom were Irish Protestants. But in the 20th Century all Irish political parties with a "nationalist" ideology, whether Irish Nationalist or Ulster Unionist (British nationalist), have been religious nationalists, and whether someone is born Roman Catholic or Protestant usually determines their form of nationalism.