I know some accelerators and angels (eg. Vancouver's GrowLab) actively seek founders from other countries - they've had mutliple startups come through from Romania for example. Also, 500Startups is working very hard to expand internationally, even launching programs in India, etc. Reach out to those organizations.
1) you should never assume the chances are small .. that sets you up for failure before you even got started. Imagine going up to a girl and saying "how unlikely is it for me to get your number?". #rejection
2) Many people have raised money outside their country of residence so it's possible. There's a few sites that are starting to aggregate investors; www.angel.co | http://gust.com | https://fundersclub.com
3) The best way to raise money is to get advice from someone who's done it before in your situation. So has anyone raised angel $ in Bulgaria? (Yes). Find them, ask for advice and do what they say.
Hope that helps.
