Comments
I think it is worth investing the time into researching and applying to US Universities and Scholarships. If you can't afford to go, then don't. But the really top schools (Harvard, Princeton, Yale, Stanford, etc.) are often free/heavily discounted for families making less than $100,000 per year. Seems like it makes sense to at least figure out how much it will cost to go.
My intuition is there is a huge boost in people's job prospects by attending a high reputation school. You'll have better professors, a better professional network once you graduate, and an easier time getting a job in the USA, which seems like a higher impact place to work than may other locations.
Doing an Oxford Math/Phil degree seems good for economics (and I know multiple people who have extremely successfully followed this route). Doing an Oxford PPE degree seems good for politics. Doing Oxford Math or CS seems good for technical AI Safety. I'm less familiar with Cambridge, but assume they have similar degrees available. So wouldn't rule out Oxbridge just because you can't major in Econ.
All of these opinions are my own and do not reflect those of my employer.
Might it be worth applying to Oxbridge for another subject anyway? (Not sure how different the options are).
Yeah my worry was that I don't know whether I wanted to go into stats stuff or policy, so I thought that if I just did Maths at Oxford I wouldn't gain enough information about which is a better fit for me to be able to make the switch into economics, which is possible but requires a commitment.
Having reconsidered, I think there are likely to be ways of learning which route I want to go down even if I don't go to a uni where I can study both, and the costs of doing this are likely to be outweighed by the benefit of attending Oxford, especially considering the responses this post has gotten.
(This means I am now unlikely to apply to American universities since I am able to attend a top uni in the UK, and the probability of getting accepted to an American one AND not Oxford is even lower [especially since the American assessment criteria suit me worse])