A trade war between the worldโ€™s two largest economies erupted this year, and technology is at the center of the skirmish. President Donald Trump blocked networking giant Huawei Technologies Co. from buying U.S. components, and put tariffs on many Chinese products. China responded by threatening to blacklist U.S. companies. The rising tension is testing a complex relationship, especially in tech where the U.S. and China are tightly intertwined through global supply chains and software that can zip across borders with the tap of a computer key. So which country has the most to lose? Who needs the other nation more?