Nationalism is defined as an extreme form of patriotism marked by a feeling of superiority over other countries.
Whereas the definition of racism is prejudice, discrimination, or antagonism directed against someone of a different race based on the belief that one’s own race is superior.
Race being defined as a group of people sharing the same culture, history, language, etc.; an ethnic group.
By definition alone nationalism is racism.
Patriotism often leads to nationalism, Patriotism is defined as the vigorous support for one’s country. Thus the line is very thin between Patriotism and Nationalism. Whereas such a strong support for one’s country leads to a feeling of superiority over other countries which in itself is a view of inferiority of people from other nations.
In reality while we might speak different languages, look different, have different religions or eat different foods. We have more in common then we think. One being we are all human, we all come from this earth. There should be no entailment based on the location of where we are born, our sex or what religion our parents or neighbours are. We all are human and should be treated as such.