Let me put it to you this way. Your step I score is better than mine was! I completely bombed the stupid thing. I'm not an idiot or anything (and neither are you) I just had a bad day. I had horrible insomnia the night before. I still remember looking at the clock at 4 am. Man, that was a horrible feeling. But I digress...!
I applied to 40 some programs (I can't remember exactly) and interviewed at 14 programs. I didn't turn down any interviews. I got some invites to some really good programs despite my score and some not so competitive ones because of it. Most places I interviewed at I just asked the PD point-blank during the interview how badly my score would hinder me. The large majority of the places told me that it really wasn't that big a deal since they obviously liked my app enough to invite me. A few told me that it might hinder me somewhat come crunch time, but nobody admitted to wasting my time and money. After all, it is their time and money as well.
It is said here and other places all the time, but I'll say it again. Your step I score is only ONE component of your application. Yes, a bad one can hurt you in that it gets you "triaged out" of many programs before your app is even looked at. That's just the breaks. You have to allow for that by applying to alot of programs. I would suggest applying to every program you would consider going to. Ask youself if you would rather go unmatched than go to a specific program. If your answer is no, then apply. Even if it means applying to 127 programs (not really but you see my point)! It is alot cheaper to apply to too many programs than it is to sit out a year and repeat the process.
Since the USMLE is only one component of your app, that means that you can make yourself competitive by enhancing the other aspects of it. I had very strong letters, honors in my EM rotations, a strong dean's letter, and I think a sincere and succinct personal statement. I had average grades otherwise, with a few honors sprikled in. On the whole, I think I was able to convey to the programs that I was sincerely interested in and suited for a career in EM. That is essentially the whole point that you are trying to get across to the programs after all.
Ultimately, I matched at my second choice and really couldn't be happier. Good luck.