Alright bro, first up. PLEAD NOT GUILTY. Remember you've got some funky decriminilisation laws in Canada as well. Go find a lawyer, just hit up the yellow pages, there are definately some that can help you.
Give NORML a call as well, if there is a chapter in Canada. They'll help out as well.
As for searching you - surrendering it to him was the best option, otherwise he could come down on you for hiding it as well. The fact that you gave it up straight away will count for you in court. And for pulling you over...well you can smell weed a mile away, maybe the cop just got lucky?
1.5 grams is sweet fuck all though, wtf?
With a criminal record, you should be able to leave the country (though I doubt something like this would be a permanent sting). It's just the US doesn't like letting people in with drug convictions.
www.normlcanada.org