There's nothing in the wikipedia article about the USA's ability to track planes. We did have a radar station in AK, which may be what you're thinking of? According to wikipedia it didn't produce useful information, and wasn't necessarily tracking the plane at all points anyway: http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007#U.S...
I don't think we've ever had the ability to track all planes in the world.
It'll take me ages to go through all the episodes of Mayday, but I'm certain in one of them the US released highly classified radar data to prevent a wider political catastrophe, and that the narrator described the source of the data was from a new type of radar that had the capability to track every plane in the world.
The series is exceptionally well researched and presented.
There's a larger list of airliner shootdowns here, and this is the only incident which seems to match your recollection: http://en.wikipedia.org/wiki/List_of_airliner_shootdown_inci...
There's nothing in the wikipedia article about the USA's ability to track planes. We did have a radar station in AK, which may be what you're thinking of? According to wikipedia it didn't produce useful information, and wasn't necessarily tracking the plane at all points anyway: http://en.wikipedia.org/wiki/Korean_Air_Lines_Flight_007#U.S...
I don't think we've ever had the ability to track all planes in the world.