Would I check "worked outside the U.S." if I worked overseas in the military or do I leave it unchecked since my employer is us based?

No, you will not check "worked outside the US" if you were stationed overseas with the military. Please make sure the check the active duty box on the "Do any of these uncommon situations apply to this W-2?" screen.

If you should qualify for the Earned Income Credit (EIC) then please ensure that you selected “Yes” to the “Did you live in the U.S. for more than six months in 2020?” question since members of the military stationed outside the United States are considered to have their main home in the United States for tax purposes.

1. Login to your TurboTax Account 
2. Click on the Search box on the top and type “EIC”
3. Click on “Jump to EIC”
4. Continue until "Did you live in the U.S. for more than six months in 2020?" screen (this screen will only come up if your earned income qualifies you for the EIC) and correct your entry.

Please see What are the qualifications for the Earned Income Credit (EIC or EITC)? for additional information.