(Western) Nationalism is the belief that one's country is superior in every way than other countries and that one's own country should benefit at the expense of others. For example, people viewing the U.S. as the "greatest country on earth", not caring about the genocides, invasions, murder of millions, and the intentional destruction of foreign nations for the benefit of the U.S.; rather they view these things as acceptable.

Nationalists also tend to be racists and xenophobes becuase they view those who aren't citizens/born into citizenship as lesser than simply becuase they aren't a natural citizen.

I can see nationalism being used by historically colonized nations to regain an identity after it has been stripped from them. But nationalism of western nations is almost always centered and racism, xenophobia, and colonialism