I just phoned Citi (international collect number) to change my address to the UK. The CSR said, "I need to let you know that by making this change, your account will be closed in 60 days. Do you still want to change it?" I cancelled the change, but then I said, "Is there a reason for that? I have other credit cards with this address listed and they're fine." She said, "There is nothing here, just this notice that if you change it, the account will be closed." So I guess it's just Citibank's policy? My USAA account has my UK address, as does my local Arkansas credit union account. So I don't know what Citi's worried about.
Mind you, my Chase account was closed last year, but I hadn't used it in about 5 years, so I wasn't too surprised by that one. Disappointed, but not surprised.