Long-range radar is a really hard problem, the working models are so expensive than the USAF and FAA struggle to afford to install them, and the military has a long history of being, uh, optimistic about the capabilities of their radar equipment when talking to the public. Saying they can detect a softball over the horizon and then failing to detect a widebody jet at seven yards is pretty much the history of the Missile Defense Agency in a nutshell.
For air space surveillance purposes, the FAA and USAF share their radar network, because neither can really afford to have their own. The radars are bespoke, mostly built by Raytheon, and replaced very infrequently (many are hitting 30 years old) due to the high cost. They struggle with detecting light aircraft and anything below 15k feet or so, which is why we need to use secondary radar for ATC purposes. Unfortunately (or perhaps fortunately, depending on how you look at it), this is basically the only general airspace surveillance measure in the US short of getting a fighter in the air to use its targeting radar.
The economics of primary surveillance radars is strange. Reliable service (the war on nines), robust filtering of false alarm (even tough multi-sensor ATC trackers have made huge strides...) more and more requirements on the 'high speed + maneuvering' kinematics (replace mil psr radars in some missions) and in the 'slow or static small rcs' (drones mostly but also helps). Processing latency is getting squeezed to 'almost impossible with COTS HW' levels and regulatory requirements only increase like mad. But you're only selling & installing what, at most 100 a year? Good luck recouping any R&D.
The entry in such a market is hard too, as ATC operators are conservative as hell, and Chesterton's fence tends to be respected a bit religiously by customers.
You're not going to see those targets with long range military surveillance radars either, maybe in the first 10-20kms, maybe. That is the actual problem with drones. Easy to build, very hard to detect with actual infrastructure. Whomever finds a way to track them on the 'cheap' is gonna make a buck. Even if you made actual, existing radars, able to track them (which would be a tall-order) it won't be on the whole range and it won't be reliable, because some of those things maneuver like crazy. Say good bye to your clean 2d/3d-with-realistic-aerodynamics Kalman filters and say hi to very high rates of false alarm...