How do I remove my interest income from my state return?

you should have a Wisconsin form 1NPR - non-resident and part-year resident form.

the federal column should be the same as the federal 1040 in the Wisconsin column only interest taxable there which probably should be zero since you are a non-resident. it can't be done through the federal or your resident state

1NPR instructions

Line 2 Taxable Interest
Column A
Federal column Fill in the amount from line 2b of federal Form 1040 or 1040-SR.
Column B
Wisconsin column Nonresidents – don’t fill in any amount of your interest except your share of interest income attributable
to Wisconsin and passed through from a tax-option (S) corporation, as reported to you on Wisconsin Schedule 5K-1. Note:
Interest received from a land contract sale is not taxable to a nonresident of Wisconsin. Part-year and full-year residents –
figure the interest received while a Wisconsin resident. For the period of time you were a nonresident, include your share
of interest income attributable to Wisconsin and passed through from a tax-option (S) corporation, as reported to you on
Wisconsin Schedule 5K-1.
Caution:
• If including interest reported on Schedule 2K-1, 3K-1, or 5K-1, only report the Wisconsin source amount of the amount
reported in the federal column.
• If you are a shareholder of a tax-option (S) corporation or partner of a partnership that elected to be taxed at the entity
level, include any interest shown on Schedule 3K-1 or 5K-1 in the Wisconsin column. Any income, gain, loss, or deduction
reported on these schedules is removed on Schedule M, line 30, 32, 80, or 82