Which of our world's continents are the most relevant to pop girls' sales and, therefore, should be considered the most important when measuring success and impact?

Europe, because albums cost 3x more here and our touring market is a lot bigger. Europe also plays a much larger role in spotify en youtube streams, and our market is increasing. East-Europe doesnt eveb have a real consumer market yet, so there's a lot of room to grow.
Single sales are way higher in the US tho.

Generally speaking, North America. We have the largest market and are pretty influential on other countries' tastes.

However, it depends on who you're talking about. For K-pop artists, Asia is the only important market. And some artists, such as Kylie Minogue, have made great careers for themselves with little to no US support.

North America in just about everything