CLAREMONT, CALIFORNIA — The United Kingdom’s decision to ban Huawei from its 5G networks has dealt a painful blow to China. Until recently, China was still counting on the U.K. to stick to its earlier decision to allow the Chinese telecom giant to supply non-core equipment for the country’s 5G networks. But two recent developments made such a decision untenable. The first was the United States’ escalation of its war on Huawei. The U.S. instituted a new sanction in May banning suppliers that use American technology from providing semiconductors to Huawei. Because U.S. technology is used to manufacture the advanced semiconductors that Huawei’s products, including 5G base stations, require, the company’s supply will be cut off, making production of its 5G equipment in the future nearly impossible. The prospect that a key supplier of the U.K.’s 5G networks would no longer be able to build and maintain its system is a far more serious threat than potential Chinese snoopi