No one is saying the process is difficult. The problem with visas is whether you have the right one. There was a guy who posted here recently, i can't remember who offhand, who went to America to fly/hour build/convert, and they wouldn't let him in when he got there because of this. Thats the worrying part of it. Getting one is as easy as getting road tax for your car. (Saying that now, have a look at this thread...
Click me There are plenty of threads here to help you out about this