[Workaccount2]

It's not JIT, it's that planning works on months advance notice like you mention is in large part because the supply chain is global and shipping takes a lot of time. When digikey has a month lead time because some component is out of stock, it often means "It's going to take a month for this to arrive from the factory".

In China, you can just go down the street to the factory.

As for shipping overnight, it's incredibly common in R&D and repair.

[bluGill]

Only if the factory in China will make that thing today. If they are one their New Year holiday (I forget what they call it) you won't get anything. If they are busy making something else you won't get anything - unless by human factors you can convince them to work for you instead of meeting their promises to other customers.

[Workaccount2]

Sure, but you don't have to wait 6 weeks for a cargo ship.

The concept of having centralized full-chain production for enormous productivity boosts is not some wild concept, it's ancient and well known. Industries have clusters because it benefits everyone in the cluster. The US has very few and weak manufacturing clusters.