In the US too you get paternity leave, it's very fishy to see someone claim they got fired for announcing that their partner is expecting. This is a massive liability.
What parallel universe are you in? There is no guaranteed paternity leave in the US. Some states may have it, and a few employers offer it, but it’s in no way a right.
In general, it is better for US employees to plan as though they had no rights (especially if they can't afford a good lawyer or wait months/years for the NLRB to process a claim, and even then only during a Democratic administration). Of course they actually have a few rights, but much fewer than in European and many Asian countries, and the enforcement/protection is pretty minimal and delayed. Most employees will just get trampled on with no real avenue for recourse, especially if they have bills due in a week or two.