Hey,
I lecture in California for a small private college i.e University so I hope I can provide some useful insight for you going forward.
Firstly, I recommend you research entry requirements for different colleges - some will openly list them others you will be required to ask admissions - do not be afraid to question them about it. Most private colleges like mine offer "rolling admissions" until a class is completely full.
Secondary, as you are not a U.S citizen you will not be admitable for tuition aid, however CA do provide other initiatives which in some cases can assist foreign students, however these are extremely limited and on a strict means-tested basis,
Thirdly, you will most certainly be required to sit either a SAT or ACT test before you apply, be careful as some (smaller) colleges will mistakenly try and pinpoint a GPA score based on your high school (A-Level) results - obviously this is inaccurate but it's due to the unfamiliarity with the UK education system some colleges use this. I would recommend explaining this to them (politely).
Hope this helps!
Dr Adams