I know this is a very old question, but I thought I should chip in for new visitors and people looking information on that specific "anomaly".
In my humble opinion answers the answer doesn't lie in immigrants in US or any other similar real life scenario.
In my experience, whenever I have a similar case of traffic coming from a specific town the reason is some kind of proxy or service.
e.g. Opera mini generates a lot of traffic appearing to come from one town. Since opera mini gets the page first, compresses it and then sends it to the mobile. So although the visitor is in India, the traffic you see seems to be coming from the datacenter town.
I have seen also traffic from Putney and the visitors patterns matches Indians living in India (not Indians in US). I know it sounds a bit as a wild guess but it isn't. I have noticed for example that visitors from Putney search for some words using the same misspellings that visitors from India use.
Generally in analytics, if there is smoke there is probably fire. If getting 1000 visitors from a specific city looks weird, it is probably because that's not what really happened.