As someone who travels to the United States from Canada on a very regular basis, this does not surprise me at all. The first mistake he made was to say that he

As someone who travels to the United States from Canada on a very regular basis, this does not surprise me at all. The first mistake he made was to say that he was "self-employed". That one little phrase, from my experience, sets off a very large red flag and almost always ends with being secondary'ed and very likely a complete entry denial. Generally, every question that the CBP agent will ask revolves around money: who pays your salary, in what currency, are you attempting to get in to the USA to find a job, will someone be giving you money for whatever reason (e.g. honorarium for giving a talk at a conference), etc. Additionally, trying to explain the concept of telecommuting to an agent is usually a lost cause. Canadians do have a slightly easier time getting in & out of the United States, but only marginally.