I am an American applying to Oxford and since most offers are conditional on APs I was curious as to how that would work out with applying to other American colleges. College decision day is usually May 1, but AP results come after that so I’m curious as to how that would all work out.
You might be getting ahead of yourself a little. Your performance in the interview will result in an offer or rejection, in order to get an interview will need to perform well on the aptitude test. If you are fortunate enough to get an offer then you will have to weigh up what you want to do, accept a US school or wait until your AP results. There is no getting around that. What course are you thinking of studying and what are your stats so far.
The students that I know handle it one of two ways: they deposit to a US college and then withdraw if they make their offer in July, or they ‘insure’ another UK university. For example, one of my collegekids ‘firmed’ Oxford & ‘ensured’ her unconditional offer from Edinburgh (you probably already know that you get 5 applications for the price of 1 with UCAS). Her cousin ‘firmed’ Cambridge on UCAS, but also put a deposit down at a US university; she withdrew her place (losing the $200 deposit) when she made her offer.
You can confirm your US offer, pay deposit, do it all, and still never attend. You just have to pull out in good time to avoid the financial consequences of leaving it too late.