That's true, but sort of misses the point. Most regions have a dominant industry, and these industries change over time. Silicon Valley, to take your example, used to produce actual silicon devices. Los Angeles used to be a major petroleum exporter. Those jobs left, but no one cared.
People argue over "appalachia" and make false promises about coal (coal is dying whether anyone wants it or not -- other sources are simply cheaper now) because it workers a swing demographic in presidential elections.
People shouldn't make false promises about industries that are not (and should not) come back. My point is that there is a huge incentive to do so, and Trump doing it isn't some dramatic change from what's come before.
People argue over "appalachia" and make false promises about coal (coal is dying whether anyone wants it or not -- other sources are simply cheaper now) because it workers a swing demographic in presidential elections.