I'm currently in the US on an E3, and while it is true that it is rather hard to get credit/insurance/a car when you first arrive, it does get easier. The trick is to start building your credit history from day 1: get a couple of secured credit cards and keep them paid. It'll take a few months for your credit history to even show up, and over a year for it to be any good, but it will happen. Credit Karma and Credit Inform (which you get for free with a Capital One secured card) are good tools for tracking your progress.
You should definitely have a decent amount of savings when you move over though, to offset the lack of credit.
This is a little off topic but need to have a whine about secured cards - I had two simultaneously with wells fargo and bank of america for 12 and 6 months respectively and always in the black. When trying to "upgrade", was then bounced for being on a temp E3 visa as part of some magical policy at both banks they failed to enlighten me to in the sales pipeline.
E3 is a nice idea but dealing with some of life's basics can be grueling in the US if you're off the system. It's not difficult to imagine how people on the street here can't get out of the hole.
Credit Unions are the way to go, no doubt, but took a while to figure that out.
Yea, it's not easy. I'm paying far, far too much for a car and insurance (can't wait to move to a city where I can ditch them) and only just got my first "real" credit card after being here for 12 months. It gets very frustrating when you're treated as a total nobody even when you have significant assets back home.
You should definitely have a decent amount of savings when you move over though, to offset the lack of credit.