The real reason why French is hard to understand for English-speakers is the numerous liaisons (that I mentioned recently) and lack of junctures between words. English tends to pause more often between words and exhibit open juncture, while French pauses between phrases and links sounds between certain word boundaries so that determining individual words is rather difficult unless one already knows French phonology. In addition, English is a stress-timed language that gives prominence to stressed syllables and reduces the unstressed syllables, whereas French is a syllable-timed language that gives equal prominence to all syllables, with the so-called “stressed” syllable always being the last.
Nevertheless, I would like to add another reason why French is hard to understand: the transformation of English words in the French language. I have nothing against borrowing since it’s a natural part of language evolution and change, but English-speakers are at a slight disadvantage when trying to learn vocabulary in French. We basically have to learn a new Frenchified version of the English words, along with the pronunciation based on French phonetics.
First of all, the borrowed words are often changed slightly so that they are not exactly the same as the original English word. Fortunately, they are quite easy to understand in writing and are usually easier to change from French to English than English to French because many times French drops the end of the phrase. However, the pronunciation of these words can be radically different and so understanding “English” words spoken in French can be a challenge. This is also true of names and titles – it took me a good 5 minutes to understand Sons of Anarchy when I first heard it pronounced in French. Usually it is the stress on the last syllable in French – which rarely happens in English – that makes the word so unrecognizable for English-speakers. Finally, since most of these words are recent borrowings and considered too informal, they are often missing from textbooks and grammar books. So once again the only way to learn them is to listen to native speech in everyday situations that has not been produced specifically to teach the language (and therefore stripped of all cultural and informal vocabulary.)
If you teach English to French students or pay attention to the mistakes that French people make when speaking in English, you may notice that they simply use the French form of the English word and assume it is exactly the same as in English. Every single one of my students thinks camping is the correct way to say campground or that bowling is the sport and the location where one bowls. So on the other hand, French students learning English are also at a disadvantage because they need to re-learn the English vocabulary they thought they already knew.
Here are some examples where the French “English” is shorter than the real English:
trench coat: un trench
parking lot: un parking
campground: un camping
bowling alley: un bowling
fast food restaurant: un fast-food
drive-thru: un drive
bodysuit/onesie: un body
e-mail: un mail
volleyball: le volley
basketball: le basket
Other French “English” words are usually easy enough to figure out even if they are rather different from the original:
sneakers: des baskets
cereal: des cornflakes
rollerblades: des rollers
lip-synching: le play-back
facelift: un lifting
celebrities: des people/pipol
schedule: un planning
bartender: un barman
tennis player: un tennisman
Though some of them are a little harder to figure out:
dry cleaner’s: un pressing
blowdry: un brushing
walk-in closet: un dressing
political rally: un meeting
makeover: un relooking
channel surfing: le zapping
hit song: un tube
music video: un clip
style: un look
lounge chair: un relax
And others have a much more complicated etymology:
tuxedo: un smoking
station wagon: un break
One tip for learning this type of vocabulary is to check out celebrity magazines online (like Closer or Public) or some TV/radio stations (like MTV or NRJ) for videos or audio. They use a lot of English words because they are geared toward young people and they want to seem cool.
Pronunciation of the above words, as well as many more “English” words used in French, can be found at French Tutorial VII.
Some of these not-really-English words are used in other languages as well, not just French. Lifting is also used in Italian and Spanish to mean facelift, though in German it means to take the ski lift uphill. Wikipedia has a page on pseudo-Anglicisms if you want to learn more of them.
Trilingual English-Spanish-French Books for Children
Books on French Linguistics and Sociolinguistics (in English)
English and "Correct" Words in French
Culturally Relevant Photos of French Objects: Learning the Cultural Significance of Words
Pour les francophones qui veulent apprendre l'américain / For French speakers who want to learn American English
Learning new words in French & English while traveling in France: Des Oiseaux / Birds