Is french an easy language to learn?
English derives many of its words from the French language. French is closely related to Italian, Spanish, Portuguese, and Romanian (the Romance languages). Any of those languages will be much easier to lean for a native English speaker, then many of the Asian, African, or Slavic languages are. In terms of usefulness, assuming you plan on staying in the United States, Spanish is PROBABLY (I am generalizing, because I do not know your exact situation) the most relevant to take up. Assuming that the huge swarms of Latino immigrants entering the United States cannot be stopped, unfortunately it may be English-speaking Americans who will have to assimilate. If you are seeking the English asolutely MOST closely related to English, then David is correct. German is closer related to English than any of the other languages.