I'd tend to go along with the bank here - in that it can be very difficult to re-establish yourself after an absence of three years. But I'd look into two other options for getting paid and transfering funds to yourself in the US.

If you will be working for the US branch or office of your current company, you might ask to see if they will pay your salary or at least some fixed portion of it to you in US dollars in the US. They can do an intercompany transfer or billing (which won't require them to actually exchange funds) and the US payroll department can handle the withholdings. (You'll have to pay US taxes while you're there anyhow.) If you don't have the US withholdings taken out by the US payroll department, you'll have to file quarterly estimates for federal and state taxes and things get complicated pretty quickly.

The other way to do it is to minimize the number of transfers you'll do in a year - no more than quarterly, better if you can manage once in six months. The transfer fees are outrageous, and you normally get hit on both ends of the transaction (UK bank and US bank).
Cheers,
Bev