In theory, this is copyright law working as designed, because there's a bajillion "Not-Actually-Happy-Birthday Happy Birthday" songs, in TV shows and restaurant chains. Creativity has nominally bloomed.
In practice it's a powerful demonstration of how copyright can make something that is really part of our cultural canon now something that somebody owns. We wouldn't be having this discussion if copyright terms were limited to something resembling sanity.
But, its every songwriters dream that their invention become part of 'our cultural canon'. ITs catch-22. This argument goes: a successful song, that always was 'something that somebody owns' by law, become public domain the minute it becomes popular?
What day is today? It's X's Birthday, What a day for a birthday, let's all have some cake!