Your state of residence is the last state that was your residence prior to your move out of the country. Please see this answer from GilbertC.
"Depending on which state you most recently lived in before your move, you may need to file a non-resident state income tax return even if you are living abroad. Do not assume that since you have left the US you are not obligated to file a state tax return. Each state has its own set of rules about whom it considers a “resident” and their own minimum filing requirements. Most states, but not all, also allow the foreign earned income exclusion in determining taxable income.
Most states will allow you to be released from you residency status if you can prove your residency somewhere else for more than six months of the year.
Only four states make ending your residency very difficult:
- California,
- New Mexico
- South Carolina
- Virginia
If you moved from one of these states, it is unlikely you have been released from your filing obligation. In each of these states you must prove that you will not return to the state. If you cannot prove this, you must file a state income tax return. They look at several different factors to determine if you may return to the state at some time. These factors among others include: property mortgages, leases, voter registration, driver's license, and utility bills."
