There are many reasons for changes in an economy... in a local economy... in a national economy ... and in a world economy. Here is a discussion of just one or two of the many factors involved.
In the 1950’s Chicago to Rockford was a hub of the tool-and-die industry and machine shops that made machines for factories worldwide. There was massive export of their product. But much of the product was used locally in the midwest.
These machine shops required workers with a good grasp of math, especially 3D geometry. Many of the workers were immigrants (legal and illegal) who spoke little English but were strong in math.
But as the 60s and 70s progressed, the education system of Northern IL was taken over by the JohnAnderson/LynnMartin type Republicans. That education system produced high school graduates who could not do math.
The tool-and-die/machine shops were unable to find competent employees. Gradually they relocated to Japan, Korea and other places. They pre-ceded the movement of their customer factories to Asia. It was only natural that the factories be located close to their supply of equipment. This became especially true as the pace of life and product cycle became faster and faster.
Consider now. Suppose you want to start a plastics factory in the US. Your plastics factory will need extrusion molding and compression molding and other types of equipment. Where will the plastics factory find a supplier company to supply that equipment?
Consider Mexico also? what percentage of the equipment in a Mexican factory comes from tool-and-die/machine shops in Mexico? Korea? China? Japan? Taiwan? the USA?
There are other factors, of course. The cost of regulation is heavy overhead. Taxes are an issue.
You are either pro American or you are a traitor.