To be technical, ASIC miner CHIP manufacturing on the 14/16nm node is in either Taiwan (TSMC fab with input or part-ownership by Samsung) or New York State of the US (Global Founderies, ex-IBM fab) at this point.

 The MINER manufacturing is largely China (Bitmain, Innosilicon, Cannan?, BW.com, some of the announced BitFury makers) but it's also spread out a lot (other BitFury miners out of the old USSR areas, BitFury itself, and at least one other US major farm in the making that has designed and is using it's own chips).


 Bitmain in particular has shown a LOT of issues with getting enough chips to make miners with- when you have LARGE companies like NVidia and AMD having availability shortages on their new cards that they plan to sell millions of, a small company like Bitmain has to settle for what capasity is left over (and keep in mind that AMD has long-term contracts locking in capasity at Global Founderies due to the ex-AMD fabs being part OF Global Founderies dating back to it's foundation and their sale TO GF by AMD - and a lot of the rest of GF capasity is locked into IBM for the SAME reason).

 

 If there is a fork that disabled any current ASIC miners, the result would be to make the coin that forked away almost worthless while there would be another coin that would take over due TO the existing miners not being able to move from the existing blockchain/infrastructure.
 In other words, if any "change POW" fork happened to Bitcoin, it would largely KILL Bitcoin in a hurry - and if it happened to Litecoin, it would kill Litecoin even faster.