In the most technical sense of how many CCA points you received for your extracurricular activities, it doesn’t matter what your score is on this for applying to top US and UK universities. However, what those points represent - whether you have been a leader in a club or society, for example, or whether you have represented the school or country in a competition, matters a great deal. Being able to list concrete extracurricular achievements in your resume or writing about it in your essay or personal statement would matter a lot. In general extracurriculars would matter more on a US application than a UK application, especially if you incorporate it in your Common App essay.