This is a new service this year and although it doesn't say if they exclude foreign users ... contact TT support for the answer and the directions. Contact TurboTax support and speak directly with a TurboTax support agent concerning this situation. See this TurboTax support FAQ for a contact link and hours of operation -https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number
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Look at the form 1040X and both the original return & the new 1040 to see the changes …
Column A should have the figures from the original return, Column C the corrected figures and Column B the differences between the other 2 which needs an explanation on page 2 of the form 1040X.
If you completed it correctly you will see an entry on either line 16 OR 18:
On line 16 should be the amount you paid with your original return.
On line 18 should be the amount of your original refund you received.
Then you will see your extra refund on line 22 OR the new balance due you need to pay on line 20