@seunkim95 you only need a tax ID ( TIN) and so , even though you are an Non-Resident Alien and domiciled abroad, for tax purposes you are treated no different than an NRA living in the USA ( at least for federal purposes ).
Thus you are taxed ONLY on US sourced income. Since you have had US sourced passive income in 2024 ( gains from sales, interest , dividend etc. ), you still have to file a return. The reason you need to tell your broker / bank etc. that your status has changed ( from Resident for tax purposes to NRA and with no US residence ), is because they need to withhold federal taxes either directly or through an agent --- US wants to make sure that the legitimate taxes are paid.
For the State, you are not a resident ( domiciled ) and therefore there may be no requirement to file a return ( you need to make sure of this by looking at "non-resident" definition for the particular state ( where you stayed last ). But generally you would not need to file a State tax return.
Does this answer your query ? Is there more I can do for you ?
