So in theory someone in Russia, China, or (fill in any country recognized the US but the not in a declared war against the US) can own and operate American Radio and TV stations?
Subject to the approval of the FCC and the DOJ. And certainly if Congress disapproves, they could pass a law about it.
As we've said, the US government and several US companies own and operate radio & TV stations in many foreign countries. For example, the government owns a radio station in Baghdad.
Both Russia and China create programming that is broadcast on US radio stations owned by American citizens. Just recently, the FCC has said the owners of those stations have to register as foreign agents, but didn't prohibit those stations from broadcasting state propaganda from those foreign governments.