Effective Modern Great Wall of USA

Thousands of miles of mostly flat border...

1 major guard station every 100 miles, smaller stations between, armed but mostly skyspy drones, quick-response teams, officials ready to rapidly ID, record and repatriate... an effective modern Great Wall of USA need not be a literal fence the whole distance.

But all pointless without the power to interdict and deport, and a nation that actively cares about its own continuing existence.