There's a big difference between buying cars from Germany and buying oil from Saudi Arabia. If Germany decided to stop selling cars to Americans, we could either buy cars from other countries or produce our own. We don't need cars from Germany. If Saudi Arabia decided to stop selling oil to America, we could try to buy oil from other countries or try to produce our own, but I I'm not sure we'd be as successful in replacing Saudi Arabia's oil as we'd be in replacing Germany's cars. We need oil from Saudia Arabia (if not directly, then indirectly through price).
The U.S. doesn't trade with Cuba or North Korea for political reasons, but that's because Americans don't need Cuban cigars or whatever North Korea produces. Some Americans think we shouldn't trade with China because of human rights concerns, but that's about as likely to happen as our refusing Saudi oil because we also need Chinese goods. As soon as oil becomes as necessary as Cuban cigars, we can expect to stop enriching nations that may not share the same interests as we do. We could also expect that a movie like "The Kingdom" wouldn't have been made because we'd be exclusively buying oil from and searching for oil in countries we didn't think were volatile.