Yes, they can just buy from existing miners, with a bit of a premium if they want the equipment fast. Also any first world government can easily mass produce ASIC equipment if they wanted to do it, there's no technical hurdles.
Hmm... the why are the vast majority of ASIC manufactured in China?
(the hurdles are perhaps more economic or social)
Because it's cheap, not because the US or Europe don't know how to manufacture ASIC.