French poses a large number of difficulties for the native English speaker. While the letters are the same, the sounds are subtly different (more precise, less rounded than English), and there are at least three sounds that simply don't exist in English (the two "u" sounds "ou" and "u", the nasal "n", the guttural "r"). You most likely won't even be able to hear the difference between the two "u" sounds until after you've trained your ears.
Also, many sounds are simply elided from the words they are attached to. Almost any word with an "s" loses that sound ("filles" and "fille" for daughter(s) are both pronounced "fee"). A word like "comment" (how), where if you were to pronounce the "ent" would be a very light nasal "n" sound, is pronounced "co-mo".
Additionally, while the number of contractions in English is small, French has a construct called the liaison (which means link), which causes a combinatorial explosions in audible contractions. For example, the word comment (pronounced "co-mo") and the word allez (pronounced "ah-lay") links to become "co-mo-ta-lay". (added "T" sound).
This link is because normally, in French, two vowel sounds can not be consecutive, and so the otherwise silent sound is re-injected to make the two sounds flow together better. In cases where no sound has been elided, a new letter is injected to keep the flow. "Has" is "a", and "he" is "il", but "has he eaten?" gets an injected "t": "a-t-il mangé?". However, if adding the sound for flow causes confusion, then the French will leave it out for no strict reason. The example given to me was "trop aidé", which translates literally as "too helped", because the link would make it sound like "too gay", which would cause confusion.
So when you combine these (along with a number of complexities I haven't mentioned yet (like there's a whole verb tense that only exists in writing, but not spoken form), then French in specific conflicts with a lot of what you learn for English, making it very difficult to learn as your second language.