Radio Orchestras are virtually non-existent in modern American broadcasting. But in the golden era they were huge. The biggst name in the US was probably the NBC Symphony Orchestra conducted by Arturo Toscanini, but the last was actually the Tonight Show Band, aka the NBC Orchestra, which was led by Doc Severinsen. When Jay Leno took over the program in 1995 the Orchestra (which was small-ish to begin with) distinctly became a band. That was the quiet ending to a long American radio tradition.
But the idea never died in the rest of the world. In Europe the BBC has at least 5 different orchestras today. Germany is really big on radio orchestras and has no fewer than twelve different radio orchestras performing classical and jazz for it's regional radio networks. Denmark has two, and the Netherlands have twice that. But in America it's utterly fizzled. the very last orchestra is the the CBC Radio Orchestra. they were founded in 1938, dissolved in 2008 and went independent as the National Broadcast Orchestra out of Vancouver. Australia has six radio orchestras, and in Japan the NHK Symphony Orchestra has been operating continually since 1951.
The world as a whole is loaded with radio orchestras. They're in Finland and France, Buenos Aires, Russia, Romania, Poland. Even North Korea had a radio orchestra until 2013. Based in Pyongyang, the Unhasu Orchestra when nine of their members were executed by the state. [SOURCE] But there are no radio orchestras on the North American Continent so far as I know that covers The USA, Mexico and canada. The nearest one is actually in Cuba where the National Symphony Orchestra of Cuba is so reknowned they have even preformed on WGBH. More here.
So it is no surprise that the rest of the world quite likes their radio orchestras. This year the Radrio Festival celebrated thew world's top radio orchestras. More here. Just two years ago the Romanian Radio Broadcasting Company began holding the festival in Bucharest gathering radio orchestras, acclaimed soloists and conductors. Sadly, America cannot even participate.