Hi Bjoorn- I spent age 0-7 in London, then 7-18 in DC and did the IB + 1 language AP and am at uni in the UK. The IB is much better for the US, but is also accepted everywhere if your plans change. You won't need AP as well unless you particularly want to add to an area of your application. The SAT I, which is an aptitude test rather than an achievement test, is only part of your application, and is not as significant as your overall academic school performance. You may do better in the SAT I if you've been studying the IB, as you have to study five subject areas for it as you know, and this isn't the case with A Levels. The SAT II subject tests are easy if you've already done the subjects at IB. As Anglo says, you can get college credit fro the IB; even the most prestigious US universities should give you 3 credits for each 6/7 at IB HL; some will give you credit for 6/7 at SL.
It's expensive to study in the US and financial aid is very unlikely. No one here in the US will write you a loan if you're not a US citizen either. State universities are less expensive than private universities and there are some very good state universities- they run about $22,000- $26,000 for tuition and fees per year.
So take IB as it will be accepted wherever you apply.