If you are a US resident you must file a US tax return. Resident (for tax purposes) means that you are a citizen, a green card holder, or a resident alien who passes the substantial presence test.
If you are a non-resident, you must file a US tax return for your US-sourced income. Non-resident means you are an alien who does not pass the substantial presence test, which usually means that you were in the United States you lived in the United States less than 183 days counting all of the days this year and 1/3 of the days last year. US sourced income generally means income that was paid to you while you were living and working in the US, and generally does not include income paid to you while you were living overseas, even if the company is based in the US. TurboTax cannot prepare a tax return for a non-resident alien, this is form 1040-NR and TurboTax does not include it. You will have to find another software provider.
If you are subject to US taxation and file a tax return, that would be the proof that you show to your home country, the completed and signed tax return.
