Many or most US med students could and do pass this test without studying.
That being said, I paid $1000 plus a train ticket to take this exam, so just to make sure I would not have to do this again , I read the first two sections in First Aid for CS, which are good for getting a sense of what the test will be like, and also for going over the "script"/format that you are expected to follow, as well as sample "challenging" questions that the SPs may (and do, in my experience)ask.
I also skimmed the minicases section to get a sense of the type of scenarios used on the test.
I felt this was adequate preparation, and I passed. I spoke with other students who did not prepare at all, and some were more nervous after the exam b/c they went in cold and were thrown by a few things at first. Now I'll bet they also passed - however, the stress-level during and after the exam may be lower for those who were at least familiar with the format and expectations.
Best of luck.