Hi Rain,
You can take a laptop with you to the US quite easily. You take it as additional hand luggage and they have separate procedures for computers at the security checks so that they don't go through the Xray machines (Which can wipe the hard drive) You will need to take your laptop and modem cable.
A word of warning though - if you use the laptop via the hotel's phone and connect to a UK server number you will probably be charged the equivalent of third world debt in phone charges. You need to either find the local number of your internet company (such as AOL) or I believe you can buy AT&T phone cards for internet.
Another way to 'stay in touch' without the hassle is to use the internet booths which are located in many restaurants. These work out cheaper and easier if you want to just check emails etc.