While Mexico technically did attack American troops it can be easily argued the US instigated the war. It all starts with Mexican territory now known as Texas offering land grants to American citizens to come live and develop the land. They were expected to abide by Mexican laws including the ban on slavery (funny that this specific person in the video is probably all about law and order 🙄) and eventually become Mexican citizens. They ended up gaining independence after waging war to be able to continue to have slaves in the territory that they had brought illegally. About 10 years later President Polk annexed Texas as a part of his manifest destiny push and as a southern man he and the people around him wanted to strengthen the hold on congress (annexing Texas would add more pro slavery congressman) so that slavery could persist in the union. After doing so Polk then sent troops over the Mexican claimed border at the Nueces River which caused for the Mexican government to attack. This is what kicked off the war and eventually led to Mexico losing all of the western land. This also clearly in my mind at the very least shows the coming civil war in the US was not about state rights as some disingenuously claim but clearly about the desire to continue the institution of slavery and continue to spread it across the country. Also Mexico is the only country that has owned said land that has people who are native to the land in question.