TAIPEI, Taiwan — As Chinese warships rehearsed a blockade of Taiwan this month, they simulated a scenario global leaders and policymakers have been busy worrying about: not war, but a grinding halt to the electronic supply chains that make the modern world run. Taiwan’s biggest trading partners — which include China, the United States, Europe and Japan — have different ideas about the self-ruled island’s political future, yet all share common ground in one desire, to expand their piece of its cutting-edge semiconductor industry. Beginning with Speaker Nancy Pelosi’s visit in early August, a succession of American delegations have kissed...