What is EC 261? The airlines would prefer you didn't know.

In the United States, airline companies are the ones to decide how to (or how not to) compensate travelers when flights are delayed or canceled. In the European Union, airlines are required to compensate travelers or pay for hotel rooms and meals, even if the reason for delay or cancellation is not the airline's fault.

How does this benefit Americans?
The law applies to all flights departing from the European Union, regardless of the airlines and regardless of the passenger's nationality. So if an American Airlines flight from any state in the European Union flying to the U.S. is disrupted, you should be compensated.

This recent NY Times article explains how you can file a claim and where to seek help if the airline refuses to provide the compensation required: http://travel.nytimes.com/2010/07/18/travel/18prac.html?ref=travel