There are potential dangers to this both from the perspective of the country to which the programs and ads are being broadcast and from the perspective of the United States.
From the perspective of the developing country, there are two main dangers. First, there is the danger that people in the country will become dissatisfied with what they have. American programs and ads depict a very wealth and materialistic culture. If people in developing countries view these broadcasts, they may come to want the things they see even though their economies are not able to supply them. This can lead to discontent among the people. Second, there is the danger that the local culture will be obliterated. As people watch American programming, they may come to prefer American culture to their own. This will make it more likely that the local culture will wither and we will move toward a more globalized and uniform culture.
From the perspective of the United States, there is only one real danger. This is the danger that people in the developing countries will come to have negative views of the US because of the programs. For example, people in religiously conservative countries may come to have a very negative view of American society because our programs involve too many things like nudity and drug use. This can help turn people against us, which is not good for our ability to make friends around the world.
Thus, there are potential dangers to broadcasting American-style programming to developing countries.