The boundaries between pop, country and western, and rhythm and blues have evolved over time and are not as rigid as they once were. In the past, these boundaries were defined by geography and race, with pop assumed to be consumable by everyone, country and western being associated with white people in the South and West, and rhythm and blues being associated with black audiences.
Today, these boundaries are not as clearly defined, and there is a greater overlap and blending of genres. Pop music, for example, incorporates elements of hip-hop, R&B, and even country and western, and many artists have crossed over from one genre to another.
However, there are still some distinctions based on geography, race, and age. Pop music tends to be more popular in urban areas and among younger audiences, while country and western music tends to have a stronger following in rural areas and among older audiences. Similarly, rhythm and blues has a large following among African American audiences, but it's also consumed by people from all different backgrounds.
In summary, the boundaries between pop, country and western, and rhythm and blues have evolved over time and are not as rigid as they once were. Today, these boundaries are more blurred, but there are still some distinctions based on geography, race, and age. Pop music tends to be more popular in urban areas and among younger audiences, while country and western music tends to have a stronger following in rural areas and among older audiences, and rhythm and blues has a large following among African American audiences, but it's also consumed by people from all different backgrounds.