Age vs career in natural science
Probably, age at graduation is not the most important factor for a career in academia. But assuming it was, then according to your estimate (30), you should be rather competitive.


  For the 2003 doctorate recipients, the median total time from
  baccalaureate to doctorate was 10.1 years, while the median registered
  time was 7.5 years and the median age at doctorate was 33.3 years.


Time to Degree of U.S. Research Doctorate Recipients 

(Being 33 and just about to submit my thesis, I'm right on target.) Also notice that with your pre-PhD degree, you are already looking back at a  a few years of scientific education that your US peers lack, if they start grad school with a bachelors degree. Academic employers know this. 

Maybe this is not a full answer to your question, but at least a consolation. Don't panic.