While abroad, you can't always rely on English as a back up to communicate. During your time abroad, you will probably use and practice another language every day; you will interact with native speakers at every turn. Even a simple task like going to the market becomes a learning experience. You pick up subtleties, authentic accents and pronunciation, jokes, stories, and local phrases you never would have learned in a language class in the United States. Most of the time, you find you are learning new things without even trying; simply being surrounded by another language day and night helps you absorb more than you think.
Another advantage of total immersion is that you not only become immersed in another language, but in a new culture as well. Initial language learning opens up more opportunities to explore the literature, music, art, dance, sports, etc… of other countries.
Total immersion also makes you more marketable in the job world, even on an international level. After learning another language, you have an advantage-an extra edge-above other job candidates. You have broadened your communication skills beyond just the English-speaking world. Your non-English language abilities are a major asset, and companies know it.
Aside from the job world, you may also use your language class credits earned abroad to add a major or minor back at your U.S. home campus. You could also tutor or mentor other students who need assistance with the language you have learned.
Each program has its own specific language level requirements. Usually, you can tell how intensive a program's course of study will be based upon its required level of language proficiency. Language requirements range from no prior language instruction, to a highest language level of nearly bilingual. You may want to check and see what prior level of language your program requires, so that you can start/continue learning another language abroad.
Aside from learning a country's official language, most countries also offer opportunities to learn other indigenous languages and/or different dialects prevalent abroad. You may want to check to see if your study abroad program offers language instruction in such non-traditional or non-standard minority languages and dialects. The study of such languages will be beneficial for those interested in anthropology, linguistics, and national security, among other professions.
In short, learning another language while abroad can help you to create global awareness, promote international security, enhance your academic learning, develop leadership skills, advance your career, and experience personal growth.