I am from Europe, and I did an internship in the US (California) in 2015. When filing my 2015 taxes, I ended up having to pay some small difference for the federal taxes, but got a refund on my state taxes, of roughly $1.6k. That was all the income I had in the US in 2016.
I did not enter the US in 2016 at all.
I managed to figure out that I don't need to file any California tax forms for 2016 (source: https://www.ftb.ca.gov/individuals/FileRtn/) but I am not sure about federal taxes.
I tried researching the problem, and got some information on it, but the situation is still a bit unclear. It seems that since I listed my state tax as an itemized deduction in my 2015 tax report, which I filed in 2016, the state refund I got in 2016 is, in fact, taxable.
In this situation, would I have to file my taxes (and possibly pay owed tax) for 2016, even though I never set foot in the US in that year, and my total income is just $1.6k?