YMMV
In general, my worst entry experiences anywhere have been with CBSA, although CBP does their best to retain their claim to worst world-wide. My last few entries have been quick and painless, but entering Quebéc from Vermont a few years ago, CBSA thouroughly searched and then swabbed all my bags be fore an agent returned and informed me that they had "discovered traces of opiates" on my bags and wanted to know if I had an explanation. Based on prior experience I knew this was a lie and I told the agent, "yes, I think the explanation is that you are lying to me in order to see how I will react." After arguing with me for a few minutes he finally acknowledged they hadn't in fact detected anything, but tried to defend himself by saying he was"just doing my job". I asked if his job description included lying to visitors; he said they had the right to do so. I told them that I also had the right to be take offence and if he wasn't prepared to deal with the consequences of lying he should work domewhere else. I was then free to go.