Script using GeoPandas that takes a list of points (trauma centers in and near California) and a polygon (California) and subdivides the polygon into a polygon per point (1km resolution).
Any point within a trauma center's polygon indicates that trauma center is the closest to that point.
Visualization: https://studio.foursquare.com/public/9aa7f827-9e11-4380-a9f9-81852ff9cd98