Resident Alien for Tax Purposes의 경우, Substantial Presence Test를 해서 Resident Alien인지 Non-resident Alien인지가 파악됩니다. 그리고 Tax filing을 2018년도 또는 2019년도에 하셨으면 나온다는거 같아요.
https://www.irs.gov/individuals/international-taxpayers/determining-alien-tax-status
You will be considered a United States resident for tax purposes if you meet the substantial presence test for the calendar year. To meet this test, you must be physically present in the United States (U.S.) on at least:
31 days during the current year, and
183 days during the 3-year period that includes the current year and the 2 years immediately before that, counting:
All the days you were present in the current year, and
1/3 of the days you were present in the first year before the current year, and
1/6 of the days you were present in the second year before the current year.