Poker tax in Oregon for a Canadian player

I may play a tournament in Oregon, and have been told by the card room that they wouldn't even withold any of my winning if I for example won $20k.
Just have to fill out a tax form.
I'm a Canadian citizen.
Does anyone have info on this?
I might have been told wrong information.

Thanks!

I am wondering if they deduct the % before I leave the poker room?

That’s what I was told