The 280 UTQG rating of the Proxes T1r is no different than the Cooper Zeon 2XS which means it's mileage is likely no more than the Zeon. The Coope Zeon 2XS, I do believe, is a USA made product. If you sense a bit of protectionism there, you are correct.
IMO: A 280 rating is low and with the forces of the RocketIII applied, this UTQG rated tire will get you maybe 250% that of a stock Metz. The "rounded" section of the Zeon led me to it in lieu of something else.
With an Eagle or other 400+ UTQG rated tire you may get no less the performance imagined with the Zeon or Proxes but 500% or more miles.