"Should I be seeing a line for GA state taxes too?"
Yes, ideally. When you became a GA resident, all your income from that point on became subject to GA income tax, regardless of the income's source. If your employer does not withhold GA state income tax for you, then you must make quarterly estimated tax payments to GA. See this:
https://georgia.gov/pay-estimated-tax
Also, if you never physically work within the state of MA, then your work income is not taxable by MA. If you will be working 100% remotely from a GA location, then your employer should cease withholding MA income tax. MA income tax does not apply to non-residents who perform no work within the state of Massachusetts.
If MA taxes were incorrectly withheld from your pay, then you may obtain a refund by filing a non-resident MA tax return, on which you report the withholding but declare zero MA income.
Your employer's location is irrelevant; the issue is where you live and where you physically work.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
