A widespread slowdown in China's economy would have major impacts on the rest of the world, but it's important to remember that the stock market is not the economy (just an imperfect measuring device). The stock markets in China have been very bubbly lately.

My (admittedly limited) understanding is that most economists are still expecting significant growth in China this year, though not as strong as previous years.

Also, the recent financial crisis in the US was partially/mostly driven by a debt crisis (housing/mortgage issues), which historically has had far larger and longer-term impacts than a stock market crash/correction.