I've been applying from abroad this year, and I agree with Ok2Panic: It's doable but physically and financially painful.
Most importantly, a lot of schools (in my experience at least) have been accommodating if you make sure to inform them that you are coming from abroad. Thankfully in my job it has been possible for me to take one- to two-week breaks every two months (October, December, and one coming up two weeks from now) to complete interviews.
The logistics involved have been troublesome, not the least having to arrange things from a different time zone without reasonable access to a phone that can call to the US. Then there are narrow time windows for flying back, and the stress of coming off jet lag into several interviews in a single week.
If you can land a job that you love and can survive in for the year AND that pays for your tickets, it's a great time in your life to pick up and live somewhere else/do something else--you probably won't have time to do this for many years after starting med school. I think it's a great experience and I would choose to do mine again. But it is very expensive and makes for a hassle.
One other thing: not that I have much experience with MD/PhD programs, but some have fewer dates available than for the MD-only students, so they are more restrictive to your scheduling. Also, for any program, sometimes invites come right at the wrong time and you have to put them off. Will it hurt your chances? Maybe.