Well, you are starting at a good age. Unfortunately there are a LOT of things that are gonna get thrown your way in the next few years. It is amazing how many top caliber cyclists just fade away as they go to high school and college. Girls, driving, partying, and homework seem to cause them to lose focus on cycling.
If you are serious. Get a bike that you are proud of and would enjoy riding for a while. Doesn't have to be top dollar, but one thats gonna make you proud and have fun riding. Get involved with a team or a junior development group, then start to race. If you put the pedal to the metal, you can have some fantastic gains in the next few years. At your age and through your early 20's... you are gonna be able to grow and recover faster than most of us old farts. If you get a little bit of success, I have a feeling it will stick with you. But getting involved early and having supportive friends and parents is key at your age.
In the US, kids dont really have cycling as a choice... for the most part. They are steered towards, basketball, soccer, football, baseball or wrestling.... or to track and cross country ( after which many make a logical change to cycling). Just grasp any local organization or group that you can learn from and see if it sticks. I certanly hope so, and wish you the best of luck.
Chris