If TurboTax "thinks" your original return was prepared as marred fling jointly --it is because you are making another user error. You have to work from the original tax return EXACTLY as it was before you filed it the first time. (and why did you say you were single if you were married...?) . If you messed with that original tax return at all-- before you began the process to prepare the Form 1040X, then you need to put it back to exactly the way it was before you began to amend.
The mistake you made might even need the help of a tax pro if you are unable to fix it yourself.
See if you can "un-do" amending and start over -- check to see what the filing status says on the Form 1040 before you start the amended return.
I clicked on “amend” by mistake
Do you now understand that all the income from BOTH spouses goes on the same tax return? Your information, your income, your spouse's information and your spouse's income all go on that same amended return in order to correct the mistake that was made when you filed incorrectly as Single.