Depends on where you wanna go, I'm assuming there's a bunch of schools that would accept A-levels, and if they are the schools you wanna go to, I'd just say save yourself the stress and do IB. However all my friends that went to the States for uni either did IB or AP (I'm guessing that isn't too big in Wales)
But yeah definitely start looking up the courses and places you wanna study and see what they require, and defo check out finance options if your parents aren't gonna be helping you out with the mad tuition over there