Exports are about 20% of China's GDP [1], and 18% of those exports go to the US [2]. So even you completely erased all of China's exports to the US, without substitution, you would only subtract 3.6% from its GDP, i.e. little more than half a year's worth of growth at the current rate of about 6.5% per year. Possibly a short recession, definitely not a crash.
[1] https://data.worldbank.org/indicator/NE.EXP.GNFS.ZS?location...
[2] https://www.thebalance.com/china-economy-facts-effect-on-us-...