How'd you get the state borders? That's exactly what I need.
That has the administrative boundaries for every country.
The relevant project from the US government itself is here: https://www.census.gov/geo/maps-data/data/tiger.html
You might want to run a simplifying algorithm on the shapes first though, they're the official boundary coordinates so there's an absurd number of points on coastlines and the like, making point-in-polygon lookups very slow.
It has the stuff for doing your own geocoding as well. You can install it as a postgis extension and run geocoding SQL queries in postgres. It's an absolute joy.