Certain AM stations are authorized by their FCC license to transmit with more power at night. It is also the case that AM frequencies (MW) can skip off the ionosphere and you might be able to hear a station thousands of miles away. It is a normal phenomenon, and highly variable depending on the state of the ionosphere, which is constantly changing with solar conditions.
Ham radio operators regularly can hear shortwave broadcast stations in Russia, China, all over the world, and communicate with 100 watts of transmit power or less, all over the world. Hell, I had a contact from North America with a ham in Antarctica once with just 100 watts and a wire antenna.
Welcome to the world of radio. Sometimes old technology is new technology to folks who are unaware of it.
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