The more fundamental question to ask is what was left of our public spaces when smart phones arrived on the scene? Public space in American cities was already heavily restricted from social interaction before the technology arrived. People were crammed onto narrow sidewalks, barricaded on one side by parked cars and roaring traffic and on the other by shops (or just walls) and eateries that were unlikely to host any outdoor seating. Even the few places that were explicitly dedicated to the public, urban parks and plazas, were by-in-large underutilized in comparison to the successful versions in Europe, where a culture of "living" in public space and more pleasant urban form prevails. I've lived in Boston, New York City, and the San Francisco Bay Area in the last year. I've lived near exemplary public spaces, such as Bryant Park and Boston Common and beautiful parks in San Francisco, Oakland, and Berkeley. People make good use of these spaces. They congregate with friends, run into acquaintances, and even meet new people. The Smart phones are as much about coordination with people and events as they are a distraction when there is nothing better to do. It's true that we might look up directions on Google instead of asking someone, but there are a lot of new social activities enabled by the phones, such as finding out that a meetup.com or some other topical social group is meeting nearby. It's also much easier to spontaneously schedule get-togethers with the combination of texting, calling, and Internet.
I think that smart phones filled a void in a delinquent public space culture. It's true that you will find peoples' noses buried in their smart phones in Europe's best places, but you'll also find thousands of outdoor cafés where smart phones are just a small piece of the action. No doubt the smart phones are lamented by some people in Europe as well, but on either continent it's the wrong axe to grind. The real enemy of public space is foremost cars, and secondly the corporate driven message that the purpose of public space is to get you from one place of consumption to another. What public space should be is a beautiful and safe place (i.e. no asphalt) where people meet and do creative things together. This can be conversation or bocci ball or musical improv. I just started reading The Great Escape by Kati Martin that chronicles the lives of nine extraordinary Hungarian Jews that all grew up in pre-World War I Budapest. They all drank in a culture of art, science, and (short-lived) freedom that was devoured by fascism and communism. It's no surprise that this golden age in Hungary happened pre-car, because so much of it was enabled by the physical form of the city.
So no more complaining about new technology when things were already so messed up. We have a huge opportunity to improve public space in part because of the opportunities enabled by smart phones. It's easier to use transit and participate in the sharable economy--where we share transportation, lodging, tools, and our time.