Hey, don't feel down as this process is only natural. Was the same for me during my first semester probably because all my life I was taught by teachers who spoke with an accent (It wasn't that I went to a bad school in India or something...went to one of the finest english medium school in India). I'd attribute it as some kind of an initial culture-shock. But once I got used to the teaching style here, made new friends and started speaking americanized english night and day, the classes got really easier...Btw, it helps if you're living on campus.