Unfortunately, you cannot downgrade the TurboTax version. You have to start a new return and choose the version in which you want to do your tax return. You can upgrade the version but can't downgrade it back to the lower version.

Thank you for choosing TurboTax.

I purchase the 2018 dowload for Canada, I need the US version.

How do i correct?

@j0128 You can request a refund for the product that you don't want, and then purchase the one that you would prefer. Please use this form to request a refund: https://turbotax.community.intuit.ca/replies/2647900