Kid from Australia, you still can make it.
Hey kid from Australia, don't worry about it. I am 18 now, I started playing tennis at the same age you did. I am from Russia, but now studying in the U.S. I play college tennis for University's team. I am not planning to become a pro anymore, however, there is still a good chance. So, you have a very good chance, I am pretty sure you can easily make to the U.S. and play college sport + you can have a scholarship. There are a lot of examples of professional players who first played college sport. By the way there is a kid on my team who is from Australia, too.
My suggestion to you, work hard every practice, no matter what don't look at anyone who does not try that hard, but still is pretty good player, and all the more don't listen to anyone. As long as, you like the game and try your hardest every practice, it will pay off eventually. And remember one thing, only hard work not talent builds up real skill.
Good luck with that.