The Green Building Council has a credit under the LEED program for using local building materials. I think their credit is under 500 miles. This makes more sense than 100 miles and is often do-able.

This is a great idea, and architects have been talking about it for a long time. It is do-able with wood construction. But nowadays much of the worlds steel come from factories in China. We would have to re-industrialize countries that have lost their industrial base. Not impossible, but economically impractical.