Right across the globe, countries which have traditionally relied on American backing are suddenly starting to wonder if they should get themselves some re-insurance. Taiwan, which is almost daily subject to threats of invasion from China, is particularly worried. South Korea, Japan, Western Europe, and Britain are all wondering if the American commitment to them could evaporate as fast as the commitment to Afghanistan has. Only four months ago, President Joe Biden sounded confident and reassuring: "We will not conduct a hasty rush to the exit. We'll do it responsibly, deliberately and safely. And we will do it in full...