In Japan I was questioned about marijuana by the police. Luckily I didn't have any on me, and I took it one step further by saying "Is marijuana this stuff?? (while making injecting needles in to my arm motion" He kinda looked at me like... "ok... you have a different set of problems I don't want to even be involved with" and left... Might work in the US as well.
I live in Wisconsin, I got snitched out when I was 17. I got tried as an adult for a quarter and a pipe and I got 9 months on a program where I got tested and breathalyzed twice a month along with 20 hours of community service. Now it's completely off my record. I don't know what county you live in but a couple counties in Wisconsin have this program that I was in and it's great. I also didn't get a fine or anything. I am 100% sure no matter what happens you are not going to jail unless you just go apeshit in court and start shooting people. Reefer madness I think they call it