None of the examples you cited have gone away. You were describing station swaps, simulcasts, and format changes.
AM listening continues to decline and many AM radio stations are struggling financially. Some have gone dark, but the stations you covered should be among the last to succumb as they are in the largest markets and are high revenue producers. I predict "standard broadcasting" (as the FCC calls it) will persist the longest in the United States and my hope is that it will be there for decades to come.
Steve WD8DAS
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