Cinco de Mayo, St. Paddy’s day, Valentine’s day, the Kentucky Derby, Secretaries day, Talk-Like-A-Pirate day, are all a good excuses to Par-Tay. The only real difference is the kind of liquor that’s served.
I get to eat, drink (at least when I’m not pregnant), and even imagine that I might be pissing off some racists. I’m not seeing anything here not to like, so far.
A lot of cultures have a holiday around now. There’s May Day in a number of European cultures, and Lag B’Omer in Judaism. The weather’s generally getting nice. But we haven’t really had a holiday between Easter and Memorial Day in the US. Maybe Cinco de Mayo fits this need.
I’m Polish-American, too, and my folks (Polish-born and raised) both are familiar with dyngus. It’s not really observed as much here in Chicago (though it exists, here is the Facebook page for it) …not sure why it took hold in Buffalo in particular. Hungary also has a similar tradition for Easter Monday.
Just Google image search “lany poniedziałek” (another name for it), and you’ll see plenty of photos from Poland observing this day.
There’s a strong theory that, had they won on 5 May 1862, the French would have went on to support the Confederate Army and effectively changed the outcome of the war. So Cinco de Mayo has that going for it as well.
Growing up in SoCal in the early 1960s Cinco de Mayo was already an all-family holiday bigger than St. Patricks. There’s be cultural heritage days for the Mexicans held in the city parks and all the Gringo families would go & see the costumes and a few years later, the low-riders. And of course by then Mexican food was pretty mainstream restaurant fare for Gringos, although few cooked it at home.
I left SoCal in the early 80s for the Midwest, where they were just barely starting to hear of both Mexican food and Cinco de Mayo as Corona’s beer advertising blitz was just reaching them. Oklahoma thought then (and probably still thinks now) of Taco Bell as the genuine article.
Although I think the mystery isn’t “why do Americans celebrate a Mexican holiday?” it’s why did they pick Cinco de Mayo (which as I understand it is a pretty minor holiday in Mexico) instead of, say, Mexican Independence Day?