JIT works just fine with stuff that's simple to make or close by geographically. Car seat covers? Many textile firms around you? Sure, do it JIT... if one of them fails or gets wiped out by a tsunami, there are ten more than can take over the production.

Computer chips? Made only in one company in china? Trying to get someone else to make them, means weeks or months of production line changes + waiting time + other customers... good luck. If they're far away (eg. china), and the transport system is fucked up, you're basically fucked up too. Even a huge company like toyota can't make a chip factory "overnight" anywhere.