TikTok is trying to tap in to shoppers in the U.S. So-called social shopping is already a huge phenomenon in Asia.

Success isn’t guaranteed—and politics could intervene. But given how effectively TikTok has already disrupted the social-media landscape, U.S. e-commerce giants like Amazon should be watching their back.

The viral short-video app, owned by China’s Bytedance, rolled out its e-commerce platform to its 150 million monthly active users in the U.S. in September. TikTok isn’t a stranger to selling goods through livestreaming and short videos. The phenomenon has been around in China for many years and Douyin, the Chinese version of TikTok, has been particularly successful there. TikTok’s foray into e-commerce has also been off to a good start in Southeast Asia over the past couple of years.

The logic of the expansion into e-commerce is clear. TikTok is already a channel where hundreds of millions of young users discover new products, particularly in categories such as apparel and cosmetics, worn or highlighted by influencers on the platform. Allowing actual sales is the next step. TikTok aims to increase the total amount of such goods sold on its platform, or gross merchandise value, to $20 billion this year globally from less than $5 billion in 2022, The Wall Street Journal reported earlier.

The growth of the segment in China is instructive: Livestreaming e-commerce is flourishing there, despite a general slowdown in consumption. Goldman Sachs expects gross merchandise value for livestreaming e-commerce in China to grow 18% a year in the next couple of years—compared with 11% for overall e-commerce. The bank expects the segment to make up around 24% of the whole e-commerce market in 2025.

And last week’s results from Kuaishou, a smaller domestic rival to Douyin, lend further credence to such predictions. The company’s gross merchandise value grew 30% from a year earlier, for the quarter ending in September. That drove a 21% increase in overall revenue and a 35% rise in gross profit. In comparison, traditional e-commerce giant JD.com increased revenue by 2% year on year in the quarter. Kuaishou’s GMV for the year ended September was around $153 billion.

Apart from taking a cut on transactions, Kuaishou’s advertising revenue—which accounted for 53% of its total revenue—also got a boost from its merchants. Revenue from e-commerce advertising grew 50% year on year in the quarter, according to Goldman Sachs.

Politics is one potential roadblock to replicating this model outside of China—and has already begun causing problems for TikTok in Southeast Asia. Indonesia, one of TikTok’s more successful e-commerce markets, in September banned e-commerce transactions on social media. That has forced TikTok to suspend its online shopping operations there.

And with TikTok already under heightened scrutiny in the U.S., the push into e-commerce could put another target on its back.

Even so, Bytedance has a proven record of tapping in to the zeitgeist of the younger generations—and rapid growth. By the time politicians get around to complaining, it might already be well entrenched in the U.S. e-commerce ecosystem, and with a bevy of youthful supporters to help fend off regulation. Dinosaurs such as Amazon and Walmart ignore it at their peril.

Write to Jacky Wong at jacky.wong@wsj.com