How can i apply for American universities?

You must apply to the U.S. government for a Student Visa. You can do this at the U.S. Consulate in your country. They will ask you what University you are planning to attend/city, and will ask you to confirm that you have enough money to pay for your education, living expenses, etc. You can apply for this at the same time that you are applying to Universities, then, once you have been accepted and select a University, yo will need to send the Consulate a copy of your University registration. Most Universitiesin the U.S. only accept 10% or fewer International students, so it is very competitive. You will need to send in your high school scores and will also need to take the SAT test. If you come from a country where English is not a first language, you may also need to take an English Language test. Check University websites for their Admission requirements for international students, and the U.S. Consulate student visa pages for their requirements.

First, you must meet all requirements for admission to a US university, including top grades throughout high school, high exam scores (usually SAT + TOEFL); references attesting to your character, achievements & abilities; proof of character, leadership, community service, talent, achievements. If accepted, you will get an I-20 form. The equivalent of US high school graduation is A levels in the UK system. Then go to the nearest US consulate in your country of citizenship and apply for a student visa. Proof of a minimum of 12 years of education (Americans have 13 years before starting university), proof of admission (I-20), and proof of sufficient funds for all school + living expenses + return transportation to your country of citizenship are all mandatory. A condition of issuing temporary NON-immigration visas, including student visas, is that you return to your country of citizenship immediately upon completion or termination of studies. Study the websites of schools you are interested in attending. Pay close attention to their estimated costs for international students (not those for citizens), and add at least 20% because they chronically omit or underestimate actual costs, especially for living expenses, plus real US inflation is now running at 11%.