Columbia is 1/10th the size of the US, and about 15% of the population. It's really not comparable.
It is just one example. Brazil, with much closee to the US population, and the same kind of national radio structure I have subscribed, is another example. Or Chile, which is as long as the U.S.A. is wide is another example.
In all cases, those countries, like the U.S.A., have national brands that advertise via national scope ad agencies. As for advertising and marketing, they are no different than the U.S.A.
I picked Colombia because it has three significant population segments, ranging from Black to Indigenous to Spanish ascendancy. It also has a variety of zones, just as the U.S. does, with different language usage, local cultures and senses of heritage.
In the US, local sales still exceed national sales for most groups. That's why they still do local radio.
In the major markets, the significant stations get most of their revenue from agencies. As a long-time general manager and owner of stations, I don't classify sales by "local" and "national" but by "agency" and "direct".
Even when you get out of the top 100 markets, you still have local and regional agency buys. And they work the same whether they come from that little "Bob Smith Agency" in Montgomery or from McCann in NYC.
The easier it is for an agency to buy a medium, the better it's chances of getting a sale.
* "Columbia" is a district on the polluted Potomac or a river in the Northwest. Not country.