If you go to a restaurant here in the U.S., and it's a customer's birthday, there’s a good chance that the wait staff will sing a song while they deliver that overpriced dessert with the sparkler in it to some slightly embarrassed diner. And there's a really good chance that they won't sing "Happy Birthday to You," that core element of American culture. Why not?
Also... you probably can't remember hearing the song "Happy Birthday to You" in a major Hollywood show or movie.
You may even have caught an oddly-constructed alternative "Happy Birthday" song in a particularly sly show.
There’s a reason.
For several years, a music publishing company called Warner/Chappell claimed it owned the copyright to the music and lyrics of “Happy Birthday to You.” And, under that claim, they extracted MILLIONS of dollars from film and TV companies and restaurants, threatening to sue for any even-close-to-commercial use of “Happy Birthday to You”.
But…. In 2013, filmmaker Jennifer Nelson wanted to use the song in a movie, realized that Warner Chappell’s claim might not be legally correct, and filed a suit against them. Eventually, the court ruled that Warner Chappell couldn’t back up its claim, and Warner later settled, agreeing to repay $14mm in fees it had charged. Jennifer Nelson even made a cool documentary about the experience: Happy Birthday: my campaign to liberate the people's song.
So can you get sued for singing “Happy Birthday to You”? Now that Warner/Chappell's claim is dead, not really... unless you sing as badly as I do, in which case a personal injury claim is totally possible.