Maybe but it's not a US holiday. US holidays are not determined by population. Respectfully, Hindu or any holiday other than a US holiday have no importance to me. I would say Most Americans don't want to have them cluttering our calendars.
So what happened was slightly over a week ago Apple changed the calendar so it was strictly secular. Then this web site was full of Christians complaining about the removal of the "American holiday" Easter from their calendar. Go figure, Easter isn't any kind of official holiday. Anyway, a week later Easter reappeared but so did a bunch of other days, this time representing the entire diversity of the USA instead of the traditional mention of only Christian events. It isn't that Apple's calendar is changing to to be a "global calendar" as davidfrommobile writes, it's the US that is changing to be more diverse and has been ever since its inception.
Your real solution:
About holiday calendars on iOS and macOS - https://support.apple.com/HT208541 - "Learn how to display holiday calendars in the Calendar app on your iPhone, iPad, iPod touch, or Mac."
Use iCloud calendar subscriptions - Apple Support - https://support.apple.com/HT202361
iCloud: Delete or hide an event in iCloud Calendar - https://support.apple.com/kb/PH2684?locale=en_US
How to add calendar events to your Calendar application for OS X/Mac OS and iOS - https://discussions.apple.com/docs/DOC-12741
I think this series of discussions provides a different perspective on federal holidays: Feb 2018 post by Michael Black - https://discussions.apple.com/message/33068171#message33068171 - "technically the US Federal Government Holidays are not national holidays since Congress only has powers to create holidays for federal institutions. So strictly speaking, the USA has no legally recognized national holidays." If you're interested in more along those lines https://discussions.apple.com/thread/8293916?start=90&tstart=0 and https://discussions.apple.com/message/33080568#message33080568 and https://discussions.apple.com/message/33081933#message33081933
I'll add a note that although Washington's birthday federal holiday was last week, this is not widely observed and in my city services such as garbage pickup continued on a normal schedule.