The Team USA gymnastics superstar grabbed her pom-poms and hit the sidelines with the team on Sunday as the very first "honorary" member of the squad.

Biles did pretty well outside of missing a couple of steps ... but given the fact she only had a few days to practice, it's super impressive.

And get this ... Biles trained with the team AFTER gymnastics practices, where she's putting in work for the 2020 Olympics.