By going after TikTok, the U.S. is expanding a fight against Beijing using Chinese-style restrictions on tech companies in a move that could potentially have enormous ramifications for the world’s biggest economies.

Washington’s threat to ban ByteDance Ltd.’s video app and other Chinese-owned apps could significantly hamper their access to global user data, which is an immensely valuable resource in a modern internet economy. Any U.S. decision on a wider restriction, which U.S. Secretary of State Mike Pompeo said would come "shortly,” is likely to be followed by a similar pressure campaign that prompted some allies to ban Huawei Technologies Co. from 5G networks.

Even if Microsoft Corp. or another U.S. company purchases TikTok’s American operations by a Sept. 15 deadline imposed by President Donald Trump, the episode is the culmination of a bifurcation of the internet that began when China walled off its own online sphere years ago, creating an alternate universe where Tencent Holdings Ltd. and Alibaba Group Holding Ltd. stood in for Facebook Inc. and Inc.