Air Iberia is one example of an airline that leaves Seville and travels to a number of cities in the United States. These cities include New York and St. Louis. The flights generally include a layover in Madrid either for re-boarding or to catch a connecting flight. This usually entails a nine- to 10-hour journey altogether if you are going to JKF in New York. A round trip ticket costs roughly $5,300 dollars.
If you are looking to take a direct flight out of Seville, you will most frequently find that you can access European, North African or other Mediterranean destinations. One option is France's XL Airlines, which offers non-stop service from Seville to the French capital of Paris; a city with far more options for departures to North America. The base price for a single adult is about 180 Euros which translates into roughly $250 US.
Your best chance of finding direct flights to the US or Canada out of Spain is in Madrid, the nation's capital. An easy way to affect this is in leaving Seville by train; Spain's national AVE rail system. The trip lasts about two and a half hours and is quite cheap with a floor-price of about $14 dollars. From Madrid you can pick up most domestic American airlines' flights. US Airways for examples offers a one-way flight from Madrid to Los Angeles, CA. for an economy-class price of $1,602.