> No re-training funds
Not exactly truthful. Most "free trade" recent agreements (past ~30 years or so) come with some sort of TAA support [1][2].
Why is it the federal government's responsibility to do these things? These are implied powers which the states have responsibility for. The Constitution does not reserve any of these for the federal government.
You can't ignore human ego, denial, and the power of convention. All one-industry towns wane when their one industry either falls or moves. People complain, panic, and some even try to move to find better luck elsewhere.
Ultimately, the largest anchor tends to be housing/property, which in the US tends to be paid for by long term debt. When a town loses its economic engine, demand to move there drops to near zero and the housing values fall underwater at the same time when people need to leave. I fail to see why the federal government should be on the hook for something like this. It would be subsidizing failure in a large way.
[1] https://en.wikipedia.org/wiki/Trade_Adjustment_Assistance
[2] https://www.doleta.gov/programs/factsht/nafta.cfm