Realistically, what would china do? If you "start massively selling US debt", what does that mean? Someone has to buy it. You're increasing the supply while demand probably stays pretty constant. But realistically, I don't think it could go below 90-cents on the dollar. I mean, who wouldn't take US government debt at a 10% discount? Compared to commercial debt from a company with way more risk than the US government, that's way better. So, are we talking about raising the US government's cost to borrow by a few percentage points for a few months?

China can't really disrupt the US economy via its debt holdings. Actually cutting China off from the US would have a far greater impact. Heck, Trump's tariffs were a tiny move and created intense disruption in a lot of industries like bicycle sales. That's not even cutting off China or anything. Imagine if smartphones couldn't be imported into the US for a year or two?

But I don't think the original poster is talking about "cutting China off" in whole. I think the issue in question is about a company like ByteDance/TikTok getting to operate in the US while Google, Facebook, Clubhouse, etc. get blocked from accessing China. If TikTok doesn't need to compete with US companies in China, but Twitter/Instagram/Clubhouse need to compete with TikTok in the US, it means that Chinese companies will have double the market to sell into.

China's GDP is around $24T and the US's is around $21T so a service like TikTok can get access to all $45T while a US-based company like Facebook can't get access to the Chinese market. If you're able to service both countries, your investment in software, infrastructure, etc. goes further.

I don't think it's about cutting China off, but rather wanting a more level playing field. When we're talking about something like smartphones, Apple, Samsung, and others sell into the Chinese market a lot and while China might do things to help its own companies like Huawei, it's open enough to placate a lot of people. That's very different from Facebook and Twitter which are banned in the country. Apple is 20% of the Chinese smartphone market.

If a US company makes the Next Big Thing in social networking, a Chinese company gets to copy it for the Chinese market. If a Chinese company makes the Next Big Thing, they can launch it in the US market as TikTok did.

I don't think this is about cutting Chinese manufacturing off. I think this is a question of whether firms like ByteDance/TikTok should be allowed to come into the US while US firms like Facebook or Twitter can't enter China.