I teach American English pronunciation to Korean students in South Korea and the one thing that I found helpful for students is helping them understand the word linking between words. It's usually the word ending and then connecting them with a new sound that makes a bit difficult. For example, "would you" sounds like "woojew" when said together. Also, Americans have a tendency to change their "t"s to a "d" sound or even eliminate them altogether. For example, "twenty" sounds like "twenny" and "batter" sounds like "badder". Some words have genuine sound changes. For example, "comfortable" sounds like "comf-dur-bul". The goal is connect all the words together easily as a fluid sound that doesn't stop until reaching the end of the sentence or a comma. This usually causes the letter changes and "exceptions". I am not sure how helpful this is but I hope it might help a little. :) Don't worry~ The more you listen and practice, the easier it gets to understand~ :)

Spoken American-English is a lot different than written English. In other words, we don't speak the way we write. One thing I notice, is that when I talk, I avoid (unconsciously) using any word more than two syllables unless I really have to. So when you practice listening, and hear areallylongsentencespokenreallyfast. try to break it down into one or two syllable words.

Hi Xavier, I sharing the idea with you. I'm a Brazilian Portuguese speaker, and trying to learn English. I can understand to hearing with audio and legend in English, so when there is not legend, my mind seems to explode, or some things like this... As American people speak so quickly, try to watch moves with legend and audio on two times. In the second time, I can understand a whole part of history.