I am not sure how the credit rating works in the UK, but in many countries it requires much more than having a bank account. It usually requires taking out loans, paying for credit card bills etc.

One of my main concerns that I would have, if I were you, is that often an Expat stay turns out to be much longer than expected. Many, MANY expats go abroad intending to stay for 1 year and it turns into 20 years.

Will you need to have a credit record in the USA? You will if you want to buy a car or a house on credit. If you have not developed a credit record in the USA while there, this could be a problem. Also, costs of transfering money internationally can be very high.

I would suggest to have both bank accounts at home and bank accounts where you live. Otherwise, everytime you buy something you will be encurring transfer costs. Many credit card companies charge you a fee for every purchase you make when overseas. You will be paying large trasnfer costs everytime you want to take money from an ATM (money machine).

If you have a bank account at home with electronic banking, you can transfer a lump sum to the US when you want and pay one transfer fee. Then you will be able to take the money out locally. You can probably also get a US credit card and start to develop a US credit record. Then if your stay turns out to be longer than expected you will not be penalized later on.