Federal law in the US mandates 12 workweeks of unpaid leave to care for yourself or someone else if your employer has 50+ employees:

https://www.dol.gov/agencies/whd/fmla/faq

However, it doesn’t separate for yourself and someone else, so technically a mother could be on bed rest for 3 months and exhaust all of her leave.

A small number of states do mandate paid family leave (specifically to care for someone else which includes new parents), but they also usually stipulate minimum number of employees at businesses.

It definitely doesn’t behoove a young person interested in becoming a parent at some point to work at a startup or small business unless they explicitly offer paid parental leave as a benefit.

Part of the reason my wife and I moved to the state we did was so that she can get an extra two months of leave with her newborn, and so our daughter would be growing up in state that offered them at least that much in the future.