ASCM defines 

Nationalism - as the primary classification/ideology that a person or group uses to define their identity(s). This can be based on a person’s nationality, religion, race, culture, ethnic traditions, political affiliation, or a combination of the above. 

Culture- as the customs a groups shares and identifies as its own. It also includes customary practices for mating, marriage, raising children, education, training, etc. In short, culture is what a group does that helps define their personality and identity.