How recent to your trip were they? I told them at US customs that I had the DUI because if they catch you lying you for sure won't get in and they checked and let me go thru.
Back about '83 me and a couple buddies shot down to get beer on a Sunday and my buddy Mike had a pot possession conviction. We all said no about convictions then they ran our IDs and wouldn't let him thru so he walked back to the Canaduh customs and waited for us while we went and got beer and gas.
Another time I went down with a buddy in his car and we smoked a joint on the way. Stopped before the border to stash our pot and shit but this idiot had a little ash tray with roaches, roach clip and papers. They pulled us over and hauled us inside for a strip search and the 3rd degree. Let us go and he headed straight out the door and while I was walking past the desk there was a tray with all the crap in it. I kinda looked sideways at the border dude and he looked at me and gave me a little nod so I scooped it up and walked out. Little nervous coming back but they didn't check us on our side. Fuck I gave him hell for being so stupid. He cried like a f'n baby while we were in custody too.
We used to drive across with two vehicles and leave one down there then go down the next day and could score duty free stuff on the way back. Just buy gas the first day so you have proof that you were down for 48 hours technically and you could buy a lot of booze and smokes etc duty free.
Out of the couple hundred times I went down over the years I only got pulled over for inspection 3 times. Had smokes or more under the back seat and they never found anything. Used to score pot from my bro-in-law down in Bellingham and bring it back. Always a little nervous when I had a pound on me but cool as a cucumber when dealing with cops or customs.