>How many Americans even have an international passport? Relatively few.
According to the State Department <http://travel.state.gov/passport_statistics.html>, 7.3 millions U.S. passports were issued last year. I can't find stats on the number of valid passports outstanding, but since passports are valid for 10 years, we can come close to an approximation by adding up the number of passports issued in the last decade - 64 million. Since some holders undoubtedly died, 50 million is a not unreasonable guess. In a country of 300 million, that's a lot more than "relatively few."
Doug