As far as staying for a year, you need to look like a reliable employee, especially in better-paying jobs. No one will want to hire you in IT, for instance, if you left your last job after a couple of months. Why spend a couple of months or more getting someone up to speed on a project just to have them leave?

I say a year because you really have to give all the seasons a chance, and get past the stage where you don't know how to do anything before you evaluate the place itself. Also, you may decide to leave Massachusetts for California, only to find that the things that were bothering you aren't local after all. I've moved overseas twice, and I think you spend a minimum of six months adjusting to the country, and you have to make your decision based on the period after that.

Why would Americans move? For a better job, to see a different part of the country, to try life in a big city or life in a small town, to not be in the same city as one's ex, because the place you live is dull, because your mother-in-law lives two doors down the street, because you thought it would be fun, because you like mountains, or the beach, or stock car racing. I've lived in Western Pennsylvania, Boston, Norfolk, central Illinois, Cincinnati, DC, and Florida. I got to choose three of those places. The others were due to marriage or school, or jobs.