In answer to the original question: in my opinion, Ben Hur will never have any achievement issues because there is zero reliance on a server (beyond the regular Xbox achievement services of course).
NBA Prelude may have one achievement discontinued at some point as it's a shop related one associated with (presumably) an online profile. That said - the workaround for the "can only play the game once" issue is to actually play the game offline, and if the shop achievement can be triggered while in offline mode, then I'd be comfortable saying that no achievement in the game will be discontinued. Can anyone confirm this?
You may or may not be able to use the same card for US currency transactions - at the very least you will probably need to enter your CC details again as a US currency source, and in my experience this only seems to work for certain locations (i.e. I can't do this in Australia, but I've heard of others in the UK for example having no problems).
At worst you can purchase a US currency code via Amazon or similar and use that to get currency you need. I personally use a separate account for US transactions, but I've heard of others using their main account, so it's up to you.