The following chart is from Dr. Ed's blog:
Tightening global credit conditions and weakening commodity prices
threaten also to depress emerging economies. How important are they to
the US? More so than in the past, but not enough to hurt the US economy
much at all. Total exports of goods and services account for 14% of
nominal GDP. Merchandise exports to emerging economies account for 67%
of total exports currently, up from about 50% in 1990. The good news is
that US commodity imports have gotten cheaper.