Halloween (or All Hallows’ Eve) is celebrated on October 31 in several countries. It has its roots in pagan celebrations for the end of the harvest season, various festivals of the dead, and the Celtic Samhain festival. Day of the Dead (or Dia de los Muertos) is a Mexican holiday, also celebrated in parts of Latin America and the U.S., to remember and pray for family and friends who have died. It is on November 1. I don't see why people get so stressed with the comparison or union of these two celebrations. They're really cool. I love them both. Why "nationalize" when you can be a citizen of the world?
The United States is made of people from different parts of the world, from different cultures and it is very likely that some cultural festivities and holidays become officially recognized, at least at State level, where Mexican immigrant population is very large.
Take for instance the recent school holidays recognized in New York for Muslim festivities that take place twice a year. Although these holidays do not affect other general official activities, schools are generally closed. This is just a very good example of how the U.S. is likely to embrace not only Mexican traditions, but other community's diverse cultures as well.
While there are millions of people in America that descend from other countries, America isn't going to adopt these people's holidays. These holidays are special to these people and their home countries, just as American holidays are to many others. The holidays are what make each country unique and special, and I see no reason for that to change. Those who want to celebrate them can and should.
I have no problem with letting anyone celebrate anything that they want to. I don't think it will become a National holiday or anything anytime soon simply because the people who run this country are a bunch of old people and they're somewhat set in their ways in that aspect. They get angry if you say Happy Holidays instead of Merry Christmas. I don't think they'll embrace a Mexican holiday anytime soon.