US was over-leveraged during the crash in 2008. People are paying less than 5% down payment or nothing or sometime even cash incentives for borrowing. Compare with the US and China, it is not really the same.
I would say Hong Kong can offer a great example. When Hong Kong property crash during 1998, it didn't really become detrimental to the economy until it was down 50%-70%. A 20% correction is nothing in China.
China has two small corrections over the last decade. One is 5% and another one is little over 10%. Basically, both times the property prices rebound so quickly. It looks very bad for the government as it was unable to rein in the property prices.
With a 20% drop, it's the developers who would be even more overleveraged and unable to complete even more existing projects.
Whilst the property construction industry does need to shrink, you don't want them all to default.
I think they can manage with a modest drop and then keep on top in preventing any property price rebounds.