Can someone change their accent (American) due to a change in environment?

It's definitely possible. Everytime I visit my family in El Paso, TX I pick up the border accent after only a few days and it takes a few weeks to get rid of once I come home to Missouri. Also I used to chat to a British friend via Skype and he noticed I was picking up his UK accent and I noticed he was picking up my Midwestern accent. Don't be self conscious about it if you're planning a trip, it happens.