This was going to be my answer. And the story of Ester is sorta part of the Christian canon right? Who doesn’t like dressing up in costume, and drinking until they can’t tell the difference between good and evil?
Edut: Dwali is starting to become a little bit of a thing, at least in my part of Pennsylvania. My daughters preschool does a Dwali day every year.
But still it piles up the repurposed drinking holidays (Mardi Gras, St. Patrick’s, Cinco de Mayo) (hmmm… strong Catholicism influence there) on the first half of the year. We need a drinking holiday in September.
Back to school day!
Feast of St. Bartholomew, obviously. We all exchange knives and flay a strip of skin to celebrate!
4-20 is pretty widely celebrated here in Oregon.
See, in PA we go for the daily 4:20 celebration.
Purim. It’s a Jewish festival that usually falls at the end of March, and involves the following:
presents
pastries
costumes
drunkenness
You know what’s funny about Diwali and Holi?
From the point of view of this American, who has known and interacted with Indian folks all my life, neither holiday apparently existed before ~10 years ago. For all I know, the writers of (the American) The Office basically invented Diwali for an episode roughly a decade ago. But since then, Diwali has had a profile – my kids’ schools do a little something for it, and the Indian people we know now seem to let us in on their celebrations.
And Holi? First time I ever saw hide/hair of Holi when some Indian friends of ours showed up at a regular ol’ American birthday party full of colored stuff all over their face and clothes. That was a mere two years ago. But since then, I see plenty of references to Holi – no local celebrations outside of the Indian community yet, though. The schools don’t seem to have caught on just yet.
So … the mystery to me is this: why didn’t the dozens of Indian kids I went to school with, or the Indian neighbors I ate out of house and home in the 1980s … how did I not get exposed to these holidays? At least hearing of them? Could there have been some kind of cultural reticence about it? Or is it maybe that some parts of India (and/or some cultures) don’t celebrate them? If Diwali and Holi are not big among Sikhs, or among folks that live around Mumbai, that would explain some things.
I’m gonna guess something along the lines of “Hello, Diwali”.
Golden Week. Why settle for just a day! It’s like spring break for adults.
It’s on March 16th, right next to St. Patrick’s Day, but what the heck…I like the idea of a Irish/Finnish two-day celebration of a couple of guys who chased grasshoppers and snakes out of their countries.
And the point of the mini-lecture on history and syncretism is…?
Especially since you seem to flip-flop between “a holiday is unlikely to be adopted, if it overlaps on the calendar with another one” to “holidays can merge and evolve, even without official government enforcement.”
The Undersecretary of Holidays is not going to look kindly on this if it makes it onto the prospectus, let me tell you—especially in an election year! 
Sorry for being insufficiently flippant & shallow. Halloween is not an “official” holiday, never has been & is doing just fine. As is El Dia de Los Muertos in many parts of the country. The question concerned “American culture”–not another reason to get the day off from work.
Please–feel fee to get back to yucking it up at those weird furriners…
*Please! *No need for that. I’d appreciate a mere “sorry” for condescension, if anything.
And I’m not exactly quite sure where you’re getting the “day off of work” angle, from my side—aside maybe from my poking fun at the fact you seemed initially to be taking an overly formal stance on how a multi-day holiday could or couldn’t adopted into mainstream American culture, around the time of an already widely observed holiday. Especially one that—as I admittedly failed to specify in my original post. Mea Culpa, MLA—I was already quite aware is both an “unofficial” holiday to begin with, and is a hideous bastardization of several different traditions, thoroughly secularized, adapted through cultural lenses, and well in the pocket of the candy barons.
(And, hell, we don’t even seem to disagree that there could successfully be some kind of “melting pot” mixture of the two holidays. I just didn’t specify how, in my one-sentence post, or properly spell out that there was indeed some overlap in themes and dates that would make some kind of mixture an almost inevitable need, should a new holiday be culturally adopted. I thought that would have been implicit enough, but you have proven me wrong. I’m very sorry, and thank you.)
But don’t worry, I’m certainly not aiming to yuk it up at any weird furriners. Just posters. 
As noted before, I personally experienced Diwali/Deepavali in Nepal, and this was in the 20th century. For the same amount of time, I’ve been tormented with images of Holi. So I don’t buy into your suppositions.
Not a big holiday but I could easily see space in American culture for the adoption of the Quinceanera. A special party for girls turning 15? Something a bit more formal that the ‘Sweet 16’ - which I go through with my oldest next weekend - would be nice and it’s the sort of thing Americans would go for.
Is this not already a thing? Maybe because I grew up in Los Angeles, but I went to as many quinceansras growing up as I did bar/bat mitzvahs.
I’d wager those were only in the Hispanic community. I think Jonathan Chance means in society at large.
Despite the sizable Hispanic community where I grew up in West Texas, I’d never heard of the practice until 10 years ago when a film by that name came out (although I didn’t see it).
Oh, good point.
A big ol’ coming of age party is a big part of specific cultures, but it *doesn’t *seem to be a part of American culture at large anymore. I wonder why that is? Sweet sixteen parties sound super old fashioned to me, but a Bar-mitzvah or Quinciniera doesn’t.
This is probably a hijack, but it’s curious. I am going to bandwagon with Jonathan Chance. Teenage coming of age parties should totally be a thing again.
I grew up in Los Angeles. I confess that - during the 1970s - I hadn’t heard about them despite half of my schools being latino.
But yes, a standard coming of age party would be a worthy thing to adopt. Right now only subcultures - as mentioned Bar/Bat Mitzvah, Quinceanera and so forth - but the mainstream has a big empty hole in the culture.
Plus, hey. It’d be fun.