US trade sanctions introduced by Donald Trump and maintained by Joe Biden have erected an insurmountable wall between Huawei and Taiwan Semiconductor Manufacturing Company (TSMC) of Taiwan. Huawei was responsible for about $5.4 billion of TSMC's revenues in 2019, roughly a seventh of the total. The US ban means that any chipmaker reliant on American technology cannot sell to Huawei without incurring the wrath of US authorities. As a major client of US firms like Applied Materials, which produce chipmaking equipment, TSMC is subject to the ban. While the loss of such a big customer is bad news for TSMC, the effective blockade is nothing short of an existential threat to Huawei. HiSilicon, its own chips business, designs the components used in Huawei's gadgets and network equipment and is far less dependent on US technology than Western rivals such as Nokia. But HiSilicon does not make chips. Those are crunched out by TSMC, and alternatives are as hard to find as a Chinese Communist Party (CCP) libertarian.