Do they?If it orbits, they can 'track' (estimate an orbital path/calculate orbital paramters) using SPASUR, otherwise, it's civilian RADARs like the ASR9's and 11's and the up-dated ARSR-4's ...Yes, they should. Yes, perhaps they once did. But do they still?
The ARSR-4 keeps an eye on the perimeter of the country (mainland).
I’d like to think that the simplest explanation is that there was a scheduled test, and that the wires got crossed in the request for the FAA NOTAM. The NOTAM is in error, and should have shown at DTG a day earlier than it did.
However, if we fired an SLBM, we’d have notified the rest of the world. The opposition has satellites too. We wouldn’t want them to see a launch they weren’t expecting. You’d think the russkies would be saying, “Da. We knew about that. Had our ‘fishing fleet’ there to take souvenir photos.”
But, I am also suspicious that our early warning infrastructure isn’t what it once was. Hard to know what to believe any more.