Re: China. I agree that a slowdown in the US will indeed adversely affect China’s economy. But it doesn’t mean that you could translate that into a short china play. The mainland Chinese stockmarket is basically still a closed market. The bear market started in 2001 and bottomed out in mid-2005 and since then has bounced 60%. This is pulling HK (there’re about 150 mainland chinese companies listed on the HK board) up along with it. There’s also money rushing into HK/China in anticipation of the RMB appreciation.
Re: Sector. Perhpas retail is one worth looking at. If consumer spending slows down, I would imagine retail would be one of the hardest hit sectors. RTH is the retail sector HOLDRS ETF.