1) Download an android app called voxox .
2) Install voxox and register an account there.
3) When you completed your registration, you
will receive a free U.S. number from voxox.
4) Just copy that U.S. number and go to Whatsapp >> Settings >> Account >> Change Number and put your number in first box and the U.S. number in second box and click on done.
5) Now, Whatsapp will send a verification message to that U.S. number.
6) Now, in your voxox account you'll receive a verification message from Whatsapp and along with verification code you'll also receive a verification link.
7) Just click on that link.
Hurrah, you've successfully verified your U.S. number and now you've a U.S. number