This question seems to come up periodically. In my experience, "parachuting" into a first-world country (e.g., not being trained in that country itself) and trying to get a job is extremely difficult. First, most industrialized countries have an unemployment problem and will be very stingy with giving out work permits. Second, in a medical field there are extra obstacles (board tests, specific training, residency, etc) and rightly so since you're dealing with other folks' health and possibly their lives. Third, unless a country is English-speaking, you better have near-native fluency in the local language because you want to make sure you perfectly understand what your patients are telling you.
FWIW, I was with the UN in a previous life and have first-hand experience with this stuff since I worked in several countries. One of those was Switzerland; one of my colleagues there had a wife who was a MD in France. She could not get a Swiss work permit to work in the medical field and ended up volunteering in a school, in a non-medical capacity.
Now, if you decide to practice in the African boonies (I was there, too) you may have better luck. But watch out for the local witch doctors, who probably won't welcome the competition...