Unless you are a diplomat, the Environmental Protection Agency (EPA) and US Customs will likely not allow the import of the vehicle to the USA since it hasn't been certified for US emissions or crash safety requirements...the best thing to do is sell it there. Now, next year, there may be other choices, but right now, you'd have to replace it with a gasoline engined version, either the 535 or 550. There may be an exemption for a diplomat, but you'd have to take it back out of the country when you eventually left, adding to the overall costs.
Now, what you might be able to do is to order one for European delivery from a helping US dealer, drive it there for awhile, then they'll ship it to the USA for you as part of the deal. There is a limit on how long you can own the car before it is exported, or you'll be paying the VAT, but buying it from the USA for delivery there, you'd also need a US driver's license and address, which could make it messy. The price is right, though. If you go to the
www.bmwusa.com website you can price it out.