I recently did a 20 month stint in Korea with my wife back in the UK, 13 weeks on 2 weeks off and it was tough.
Unfortunately I committed to it before we found out my wife couldn't return to Korea due to some visa issues but as the Oil and Gas market isn't great right now my alternatives weren't very good.
Yes I made some good money but its now sat in the bank or over payed on the mortgage cause i don't feel secure enough with the work environment right now to do what i want to and buy a expensive new car etc.
With a 8-9 hour time difference even skype/facetime calls don't make up for much and it was very hard on our relationship. Wifes/GF always think work trips away are holidays unless you have had to do travel with work it sounds like fun even when its really not. That and my mother passed while was in Korea and being thousands of miles away while that happened all of a sudden was a terrible experience.
It was part of the reason I didn't do the follow up assignment (the other reason being its in Iraq but that's a whole other issue), I needed to dedicate more time to my wife to make good on the time away.
3 months its fine but if your work is anything like mine then it cant turn into 6 or 16 very quickly.
As for living/working in the US. CHECK THE PACKAGE CAREFULLY. Tax, Medical, what allowances you get (accommodation subsistence travel etc), location. Where in Mississippi? I spent a fair amount of time in Mobil, Alabama and Baton Rouge, Louisiana and had a good friend who worked at Pascagoula, Mi, the deep south can be quite a culture shock for a Brit, the food is AMAZING but your don't want to be taking a public bus to work.