Assyrian nationalism means that there are people who believe that the Assyrian people are a unique group of people with their own language, culture, and history, and they want to protect and promote this identity. Just like how you're proud of your family and your traditions, Assyrian nationalists are proud of who they are.
A long time ago, the Assyrian people lived in a place called Mesopotamia, which is now modern-day Iraq. They had their own powerful empire and their own language called Akkadian. But over time, other groups came in and took over, and the Assyrians were pushed out of their homeland. Many Assyrians moved to other countries, like Syria and Lebanon. Today, there are Assyrians living all over the world.
Even though Assyrians are scattered all over the place, they still have a strong sense of identity and community. Assyrian nationalists want to make sure that Assyrians don't forget their history and their culture, and that their language is preserved. They feel like this is really important because their traditions and language are what make them who they are.
Some Assyrian nationalists want to have their own country called Assyria, where all Assyrians can live together in peace and freedom. Others just want to make sure that Assyrian culture is protected and celebrated wherever Assyrians live.