I am informally connected to a growing network of clergy partnered with people from other (or no) religions. These brave souls prove every day that you can be a passionate leader in your own religion, and love someone from another religion.
American Jews have the highest proportion of college-educated adults in America. The assumption of many parents is that their child will enter the legal, financial or medical profession. Entering the clergy deviates from this pattern. A rabbi is simply not a popular job for American Jewish boy.