very interesting! So US refineries that can handle heavy crude are unable to handle light crude?

It's not that they are unable to entirely, it's that they are unable to economically. If you're paying more to refine your oil than what it costs to sell/use it, you're taking money away from your industries that depend on oil. Eventually the businesses would go bankrupt. Since we have a "free market", the market doesn't want to lose money, so it will run at a shortage with high prices, or stop running entirely (whole refineries can shutter due to losses). We saw this in practice during the 70s when OPEC forced a shortage. We are still vulnerable to the same thing.

The same shortages seen in the 70's would have already happened this year due to the Straight of Hormuz - except China saved the whole world from shortages by cutting its own imports of oil by 50%. Their massive drawdown created a buffer in the world oil market that everyone else pulled from. This is why China's oil reserve and non-OPEC imports make them the most powerful country in the world now. They effectively exist in a separate oil system with plenty of capacity for themselves, while we remain reliant on OPEC.