To be very frank, I don't think all the three parameters stated by you, i.e., (1) a strong resume, (2) US certification in HR, and (3) volunteering work, will have great weight in grabbing the HR job, selection of which will be based on talent/intellectual levels.
The above-stated three points make an excellent addition to your personality, which, of course, anybody will largely appreciate when you appear before an interviewing officer.
I do not know much about the 'HR course in the US,' but knowledge-related issues in India, like labor laws, the Factory Act, the Shops & Establishment Act, PF/ESIC matters, and many such subjects, which HR is supposed to be well aware of, I think are totally different from US studies.
I hope, since you still have time to come back to India, you may start preparing yourself by looking at the Indian rules, regulations, and various aspects, so that when you get an opportunity to work as HR, you will be very comfortable and successful.
Comments by Mr. Simhan, Super Moderator, are very valid and carry good meaning. My personal thanks to him.