Well, here in the U.S. the English language shouldn't be difficult to learn at all because the person/people trying to learn it would have so much exposure to it, that it'd be really easy to pick up gradually and eventually become fluent.
Even though I remember my high school Spanish teacher saying that "English is one of the hardest languages to learn, and if you can learn that, you can learn Spanish." (I never did like her)
Anyways, if you're trying to learn English in Saudi Arabia or something, I think that it'd be a lot harder since you wouldn't have much exposure to it at all.