China, Canada and Mexico were the top U.S. trade partners in 2015. Total trade (the absolute sum of exports and imports) between the U.S. and the three countries represented 48% of total global trade for the U.S. The U.S. ran a trade deficit with each of the top 10 countries by total trade, and came closest to parity with the U.K., where the deficit is $219 million. The $337 billion trade deficit with China is nearly four times larger than the next largest deficit - Mexico with $89 billion.
The proportion of total trade between emerging and developed markets is about even, with emerging markets slightly higher. The most significant difference was that the U.S. exported $85.5 billion more to developed markets and imported $138 billion from emerging countries.
2016 data are not yet complete. Through August 2016, total trade between the U.S. and China, Canada and Mexico was just over $1 trillion, representing 43% of U.S. trade with the world. The trade deficit was $215 billion with China through the end of August and $494 billion with the world as a whole.