Federally mandated parental leave (paternity and maternity leave) polls at about 80% in favor with the US adult population. This is regardless of political affiliation, by the way. Democrat and Republican voters both support it.
Upon reading this, you might be surprised as to why it's NOT federally mandated given how popular it is.
One group it's NOT popular with is corporations. And corporations donate a lot of money to politicians. And it's cheaper to donate to politicians who are against parental leave than it is to pay people for that parental leave.
I enjoy sharing this b/c it's a reminder that there are groups who spend a lot of time and money to get their way. At first, that might feel overwhelming. You might be surprised to know that when you call your local congressperson, those calls gets tallied b/c they want to know what their constituents care about. So give them a call and let them know.