If you think about it you would realize the difference. The examples you cite are flags displayed at cultural events as show of heritage. The Mexican flags held by at political demonstrations demanding the right of Mexicans to defy American laws is a show of allegiance.
You cannot site one example of an American court citing a Mexican immigrant as an illegal. I, on the other hand, have case after case of just the opposite. Example: A New Mexico rancher lost his ranch to an immigrant because he abused that person. This was done in an American court room. Canada, UsofA, and Mexico, since NAFTA/CAFTA have "common" citizenship. This has been accomplished under Democrat and Republican Presidents.