Spanish is the second most widely spoken language in the world. That is, after English, Spanish is spoken as a first and second language in more countries than any other language. Granted, Mandarin is spoken by more than a billion people, but the vast majority of its speakers reside in one country, China. Spanish, much like English, on the other hand, is spoken by native speakers in 21 different countries, as well as by many Americans and Europeans as a second (or third or fourth language by Europeans).
In the United States, Spanish is clearly the second most important language, and is continually becoming more and more prevalent in advertisements, television commercials, etc. If you live in the United States and plan to do any type of business, or simply want to communicate with more people, you really need to know Spanish. This is a trend that will not be reversed -- Spanish will continue to become more and more important in the United States in commerce, advertising, and marketing.