Below is the list of the largest trade partners of the United States as compiled by the US Census Bureau. The United States has a bilateral trade deficit with 12 of the 15. So I have ranked them according to trade deficit, with China in first place by a country mile. Mexico is second, while Japan and Germany are third and fourth respectively. (With the EU as a whole, the US had a trade deficit of $80 billion). The list also includes oil exporters like Saudi Arabia and Venezuela, but the lion’s share of the US trade deficit is in goods and services.
UPDATE: To give a fuller picture, I sorted the 2010 data for all countries and areas by trade deficit. Below are the resulting charts. Note that the US has large deficits with the Pacific Rim, NAFTA, OPEC and the European Union. The US had a trade deficit with 86 countries and a trade surplus with 147 countries. The largest surpluses were with Hong Kong at $22.2 billion and the Netherlands at $15.9 billion.
Sources: Wikipedia, US Census Bureau