The Ngram shows that in American English used never to transpired less than 50 % as often as didn't use(d) to in 2008, and its use has been steadily declining.I'm used to saying "I am in India.". But somewhere I observed it explained "I'm at Puri (Oriisa)". I wish to know the dissimilarities amongst "in" and "at" during the above two sentences.This