The correct answers to these open questions are the following.
I think some have defined nineteenth-century nationalism as a "secular religion" because it was so ingrained in people's minds that seemed like they professed a religion with their nationalistic ideas. Those nationalistic ideas were so ingrained that people defended them at all cost and were the cause of many differences, and conflicts, even wars.
I don't think this could be viewed more as a God-given right or power because God did not do these things. I considered that people felt they deserve to be more and have more. That is why they set these boundaries and did not accept other nations' culture, language, history, and traditions,
Regarding Guisseppe Mazzini, I think he can be considered nationalistic. An important Italian political figure of his time, he was a supporter and promoter of the revolutionary movement in Italy that tried to unite the dispersed territories.