The semiconductor chip shortage is old news, but when the second-largest public company in the history of the U.S. stock market says it just left $6 billion in potential sales on the table as a result of limited chip supply — as Apple just did — it reinforces why the U.S. economy needs to rethink how it sources its semiconducting technology so that doesn’t happen again. This short-term supply chain phenomenon will pass, but tech executives and policy advisors say the future may be one of even larger, longer-term supply chain shocks. A shift from decades during which the largest…