This is such a cool question! Here's my perspective. DECIDE THAT YOUR STORY IS DIFFERENT. Instead of looking at those other people and thinking "well they are successful because they got to leave," DECIDE that in this life YOU are going to be the example for all those that are watching YOU of someone who made something AMAZING with his life and never had to leave Nigeria to do it! I mean one day you may be traveling the world talking about exactly THIS. Your story is cool BECAUSE you are different and I can tell by your question that you are unwilling to settle for the way you have seen other people live. DREAM, and imagine what your life might look like if you were the man that wrote a NEW story, his own story. Imagine all the people you would inspire?? WHY NOT YOU?!
Read book, listen to podcasts, and go seek out stories of people who didn't get to go to the US and STILL found "success" and happiness in their lives. I'm thinking of a book by Kute Blackson called "You are the One". Give it a listen or read! He also has a podcast.