I can understand that. Although in the U.S. Justice System, I would argue that the public at large does not have a mistrust of authority, especially certain demographics. This is what makes others of us so mistrustful, because there is a cheerleader mentality when it comes to crime and punishment in the U.S.. Just look at the death penalty, lots of people are adamantly in favor of the death penalty, and they rally behind it when someone is about to be executed. Yet the U.S. is virtually alone in the Western world in terms of capital punishment. Another example is juries. Generally, jurors (despite instructions) tend to trust the state more than the defense. There is an emotional, underlying belief that the state would not bring someone to trial if they didn't have evidence that he were guilty, and that the defense will do anything to block that evidence. This directly undermines the "innocent until proven guilty" presumption. Jurors must overcome this in order to find someone not-guilty.
The other thing that the adversarial system creates is a measurement system not based on justice but based on convictions and case resolution. It becomes much less important to ensure that the right person is put in jail, but rather the incentive is to put the most likely person in jail regardless of guilt or innocence. From the outset, there was a belief that Brad was the most likely person, and that is reasonable. But there were also a lot of red flags that all was not right with the investigation, and it started the day that her body was found when other possibilities were irresponsibly ruled out. Had the justice system been looking to find justice rather than close the case and get a conviction, the investigation may have taken an entirely different path.
Thus I can understand why in Canada, with a system that is less adversarial and more justice-driven, a conviction in the U.S. is assumed to be valid and therefore no controversy. Each system has its benefits and each its flaws. I don't think either are perfect. But given the perspective that you presented, which I hadn't really considered, I can understand why it is not controversial.
Just gotta ditch that whole Monarchy thing