I initially forgot to indicate the amount of the interest that was deductible for Wisconsin. I amended my returns in TurboTax to reflect that a portion of the interest was from Wisconsin. When I completed amending my return in TurboTax and saved the results, there was no change to the "State and Municipal Interest" line. It was not reduced as expected by the amount of Wisconsin interest.
Generally, interest earned on state and municipal obligations is subject to Wisconsin income tax and should be included as an addition to federal adjusted gross income on your Wisconsin income tax return. However, interest earned on specific state and municipal obligations is exempt from Wisconsin and federal income tax. For a full list of interest that is and is not deductible, please see this link.
Verify what kind of interest you are reporting. Some interest may need to be added to your WI return and any interest excluded from your federal income was probably excluded from your WI state return also. In that case, no adjustment or amendment would be necessary.