Does anyone know if there is a US airline program that lets you redeem miles on Cathay Pacific?

AAdvantage

And Alaska Airlines Mileage Plan

Just to clarify: While you can redeem AA miles on Cathay Pacific, you can only do so over the phone. (I presume it's similar at Alaska.)

British Airways Executive Club. Accumulate miles on BA, AA, AS, redeem on CX.

Have I missed something rather significant concerning our national sovereignty??

You have to join BA EC first. Not so easy.

Well, it's a US program run by an overseas airline. BAEC / US has terms different from UK or rest of world. It is indeed semi-difficult to join but redemption is easier than with many Stateside programs.

Redemption may be easier (CX online) but beware that it may also be more expensive (both somewhat more BA miles than AA miles for the same award in many cases, and much higher "fees" since BA adds $$$ fuel surcharges to awards but AA doesn't).

If you're going to earn BA miles much faster than AA miles (say, because you'll use Diners Club and the "annual" 50% bonus offer on transfer of DC points to BA miles), that may make up for it, but if you want to earn a lot of miles by churning the FFP's credit cards, Citi (which supports AA) still allows that while Chase (which supports BA in the US) doesn't.

So it all depends a lot on the specifics of how the OP will earn those oodles of miles you'll need for a CX flight (all the way from the US).

You can enroll here:

https://www.britishairways.com/trave...l/public/en_us