You officially can’t use TurboTax online from a foreign country. Some people claim to have found a workaround, but I won’t recommend it here. You would have to purchase a copy of TurboTax to install on your own computer as a CD or download. You might be able to buy a download or CD from Amazon, but they may also not be allowed to sell to a foreign country. You may need to have someone in the United States buy a box copy and ship it to you. Then, you will have to get your refund by check in the mail, which may take longer as you are overseas.
I always recommend that people keep a US bank account and US credit card, for as long as they have any financial ties it all to the country. But that’s up to you.