Various jobs are avilable. These range from working in the kitchens to taking care of the children. Any nationality is able to apply so long as they are able to speak English and can attend an interview in a country in which CA has interviewers. Look at the following list of NGO's to get more ideas. Do be sure to check what you are required to pay in the way of fees and whether you will receive accomodation and food.
Programs vary greatly.
Some appear to be slave labor schemes whilst others provide a valuable cultural and work exchange. Before you travel to the USA, be sure that you are aware of the visa that you will require. You can find such information on the website of The American Immigration Center . There is also a customer service section and a document preparation service. The scope of this article has merely allowed me to touch the tip of the iceberg.