Many products have huge production chains with thousands of suppliers around the world. If there is a disaster today, I'm pretty sure we'll lose all knowledge o

Many products have huge production chains with thousands of suppliers around the world. If there is a disaster today, I'm pretty sure we'll lose all knowledge of modern inventions in a few generations and revert back to a medieval society. In theory, humans can rediscover that knowledge in a few centuries/millenniums. However, it's also possible that we'll never regain that knowledge since we've already exhausted natural resources on the surface. Without easy access to iron/coal/oil, we wouldn't be able to create machines that we have today to extract resources deep underground.