American universities accept applicants from different education systems (IB, A-Levels, AP or a national school certificate). What matters most is your academic performance and how you stand out in your school. What really counts is studying at a strong school (the best one available to you), being among the top students in your class — this shows your motivation and abilities — and having high grades and a rich profile (olympiads, research, extracurricular activities). The IB, A-Levels and other systems affect your level of preparation, but are not the deciding factor. Choose the one in which you can shine brightest.