The dimensions of the Panama Canal have shaped the international shipping world for more than a century. The width of its locks have prevented ships wider than 33.5 meters (so-called Panamax ships) from utilizing the Canal, though a Canal expansion plan slated for completion in 2016 will accommodate larger ships (up to 55m in width). The theory is that the expanded canal will encourage Asian container ships to push on through Panama in order to directly access to the U.S. Gulf and East Coasts, rather than decamp in California and truck their loads across the entire country.
Yes and no. While many ships undoubtedly will do just that, there are three complications.
First, very few East Coast ports can even accept the new Panamax vessels. Really only two: Kingston, Jamaica, and Savannah, Georgia. Typically Kingston accepts the large vessels and reloads the containers on to smaller shuttle tankers.
Second, cargo shipping is all about efficiency, and as big as the new Panamax vessels will be, much of the shipping industry has already moved on to use even larger vessels. Such vessels must continue to use the West Coast.
Third, it is highly likely that there will be a breakdown in global trade in the not-too-distant future, rendering a great deal of this moot.
For more on how the global system is shifting away from global trade, see Chapters 9 through 11 of The Accidental Superpower.