I am international student on F1 visa in the US, and been here for almost four years
Generally, when I file my taxes, I claim to be a non-resident alien. Generally, a person who spends most of their year in the US is considered a resident alien, with the exception of students (and a few other categories).
However, if I wish to set up an account on TreasuryDirect, or an online Brokerage account at my bank, they ask me to check a box saying that I am a US Person. Am I allowed to check this box and go ahead? If I do so, am I obligated to file my taxes as resident alien from now on?