*There are American universities that offer financial aid for foreign students. This is basically a waiver of all or part of fees and room and board costs, aka institutional aid. Foreign students are not eligible for US-government sponsored loans (Perkins and Stafford) that American students may be eligible for depending on income.
Awards of financial aid to international students can be based on merit or need or other factors determined by the university. 'Merit' means exceptional merit in most cases (the next Einstein)..
If you google American universities individually with a search term like 'Vanderbilt University international student undergrad financial aid' you will most likely find out each individual university's individual situation.
This is a partial list of universities that give financial aid to international students.
Top ten international student financial aid universities
*You can get a J-1 visa that entitles foreign university students to work and travel during the summer months in the US. This is perennially popular among Irish university students. Term-time work-study programmes under which students can get a campus job are not open to international students as they are federally funded afaik. If an international student wanted term time emloyment, he or she should check the terms of the student visa very, very carefully.
The advantage of A levels/AS levels is similar to that of AP courses for American students -- yes, you will be doing core courses or general education required courses in a US university in your first year, but you will not be taking those courses at 100 level if you have a 5 or a 4 on your AP exams, or excellent results in your A levels.
*Geography is unknown as a subject in either US high schools or universities. The closest you might get to it is social studies in elementary school or earth science/environmental science/biology/sociology in high school. Some universities offer Geography majors.
*The disadvantage of the A level system for British applicants to American universities is that a prospective student who gave up maths at 16 would be faced with possibly mastering Calc 3 before an American university would let you graduate. Or for a student who thought his days of English Lit or composition or foreign language were over, think again. Good US universities turn out graduates who can use statistics, read and write effectively, and are versatile.
*An example of a Wellesley's offerings for majors. (Wellesley is a women's college).
University of Chicago majors offered
Core curriculum at Univ of Chicago aka 'where fun goes to die'.
Unofficial at Univ of Illinois Champaign Urbana
no drinking my eye..
*I think he would need to have started earlier on the path to the ACT and SAT and SAT subject exams but I may be wrong. Be aware that US students commonly do test prep courses to try to squeeze a few extra points out of their tests.
ACT and SAT
*Collegeboard.org is the website to use to find out pretty much all you need to know.