The good thing is that just about anything in the world in which you are interested - science, pop culture, sports, etc - is reflected somewhere on TV or online. The keys are 1) narrowing down what exactly you mean by "pop culture," which is a very broad term 2) getting to know the people in your area really well so that you not only know the subject matter, but the necessary people will gravitate to you 3) figure out a way to make yourself unique. What makes YOU and what you bring to pop culture indispensable enough that an employer would say, "I MUST have Julia do this." Remember, there are practically endless YouTube "stars" and personalities out there from whom to choose. How do you cut through the clutter?
That said, there are limitless stories to be told about people in pop culture. The key there is "people." Regardless of the subject matter - sports, mathematicians, singers, etc - ultimately all of journalism is telling stories about people. Therefore, you can merge any subject matter about which you are passionate into a storytelling career. Go tell their stories!!