The last time USA had extended deflation, the Great Depression happened. When people stop consuming, retailers fire their workers. Then fewer people can consume, so more people get fired. This goes on enough, then its not just stores who fire workers, but it trickles to factories, R&D, office workers, etc. etc. The longer deflation happens, the further it spreads and the more people lose their jobs.
Ever since the Great Depression happened, US Policy has been strongly anti-deflation. Our policy is to “err” on the side of slight inflation.