This is just a public procession for Ashura, mourning the martyrdom of Imam Husayn. It is why we wear all black. I am a Shia Muslim from Texas.

Here is my favorite latimya (Ashura lamentation) recording, it is a beautiful poem about oppression and injustice.

https://youtu.be/ayo4JwJkjos?si=t3QVxtRG-PyCMUZS

I think it is fitting that Ashura falls on July 5th this year given that it laments oppression and July 4th celebrates a revolution against oppressors. Shias are the enemy of tyranny and the friend of the oppressed.

Imam Ali was the first Caliph. The Caliphate was usurped for the interests of selfish men, and Imam Husayn gave his life for the oppressed against tyranny.

Imam Husayn fought at Karbala alongside Christians companions as well. Even in ancient times, Shias fought holy Jihad alongside Christians. As they do in Lebanon today in Hizb Allah.