I can't see why it would be any more difficult for an American over any other nationality, there just aren't many of you here! :) Don't let that put you off though, I work for a company that actively seeks out overseas workers because there just aren't enough techs here to fill the available positions.... every company is constantly looking. Some companies, like the one I work for, are on the NZ Immigration Accredited Employer scheme which makes it easier to get a visa or residency.