If you want to buy ASIC make sure you get a brand new, make sure all components are included as well, buying used ASIC miners are risky and they aren't something anyone can repair themselves, it's why I decide to quit dreaming about ASCI miners cos no one is qualified to repair them in my country, I just stick with GPUs only
Bitmain does provide warranty for their ASICs and they do have a USA warranty address. I think years ago it was a pain because the ASICS were much cheaper back then and the shipping all the way to China would sometimes not make sense, especially when you factor in the lost revenue.
However now you can send it to California somewhere and the turn around time should be much quicker. I also think it matters how it broke. If you got lucky and its burnt, then obviously they won't repair it but send you a new one. However if the hashboard looks fine, then they might take a few days to diagnose to test a few components here and there and this is what wlll be time consuming.
Its the same with GPUs. If the GPU is burnt, they send you a new one. If there is some minor components that is acting up, they might just replace that MOSFET or Capacitor and send you back the original PCB. Happened with me many times. They don't always send you a new video card.