There are 9 drones that patrol the CA, AZ & TX border regions on a regular basis.
Been doing so since 2016.
"Border control authorities, vigilantes, and criminal organizations use drones to track
movement across the US-Mexican border"
https://www.albany.edu/~rk289758/documents/Koslowski&Schulzke_Drones_along_Borders_ISA.pdf