[MperorM]

Trade agreements don't need to be symmetric to be beneficial for both parties. Even if China didn't buy a single American good, it is beneficial for US to sell to china.

Export is what you pay for import. If China sells goods to US they will get dollars in return. These dollars are worthless except for buying American goods.

Even if China can't buy American goods, they can buy some other country's goods using their newly acquired dollars. Eventually someone somewhere will use those dollars to buy American goods.

[tooltalk]

Sure, the USD is the world's reserve currency. And, while it's also the currency of the international trade, the US's share of China's import isn't as significant -- in 2019, China imported over $2T, or $2,000B, worth of goods and services globally and, of that, only $163B, came from the US. In fact, the US is not even the biggest import nation, it's South Korea, followed by Japan and Taiwan.

[nradov]

Those dollars aren't necessarily used to purchase American goods but rather to acquire ownership stakes in American assets.