Some of them from previous years, subject specific, are available online. Apparently All Souls has the most challenging because they're the most abstract questions

https://www.independent.co.uk/student/oxford-university-has-world-s-hardest-test-here-s-how-answer-questions-a6722231.html

The only open test site for my DC last year was in Cary, lol! Had to take two exams because applying for a joint course.

Be very aware of that 15 Oct deadline. Make sure that personal statement is 100% academic, no navel-gazing.
Good luck

CollegeConfidential in the UK forum has some threads.

You can apply to several UK schools through the US common app, in which case AP scores and SAT matter. But Oxbridge each have separate entrance exams, and the tests are different for the different disciplines you choose to study.

Did not realize there was an exam. Thought they looked at US student AP test scores?

Would love to hear any first-hand experience of taking the Oxford entrance exam for an undergraduate degree from the United States. Did you score high enough to get an interview, and then get accepted?