In most countries, taxes are based on physical residency. Non-citizen is an immigration status, and non-resident is a tax status. If you move away, you become a non-resident and stop paying local taxes, even if you are a citizen.

The US bases taxes on citizenship, and is an outcast as the only country in the world that forces that. The only other country that comes close is Eritrea, but that levies only a flat ~2% "diaspora tax" on the income of its citizens living abroad.

A US citizen must report global income to the IRS no matter where they live, meaning a US citizen can never be a tax non-resident. In the US, the non-resident tax status only applies to non-citizens who live abroad.

So on the subject of investing, whilst most countries use the term non-resident, to get a close equivalent in the US you really need to use the term non-citizen.

- Manlobbi