Canadian here.
I did just as well in Math as just about any other topic until University and Calculus hit. High school calculus was fine, and I had a great teacher.
University became a different story. Each week we had a different formula to memorize, which consisted of copying the basic theory and copying the process in class, then being assigned several problems on the formula for next week.
I failed the course twice, hitting in the mid to high 40s both times.
The problem was not the basic formulas themselves, but when they started getting combined in unfamiliar ways, particularly whenever trigonometry and calculus were combined. If the formula was unknown, trying to recall a 3-hour long note on the procedure was difficult at best, and trying to build something up in what I thought was logical resulted in the incorrect answer.
Now this could have been solved with taking more time with the homework, or going to the professors and working through difficult problems.
The sciences, it felt like the process could be visualized and understood more (speaking as chemistry and biology, I had a difficult time with more advanced physics in high school, and never had it in university), where as math had you working with more abstract concepts, and things worked this way because your professor said so, and that you needed to solve it with a calculator almost all the time, which hid much of the process.
I'm going to go out on a limb and say it is calculators that cause much of the gap. the focus is on knowing what buttons to press and in what order, where as other areas there isn't this technological shortcut that hides the process (at least not that I encountered). I never reached that "click" moment where everything falls into place and it all makes sense. More time invested in math would likely have provided this, but since that moment had occurred with the other subjects first, it felt like math was the outlier.
In addition, there wouldn't be any specialized math courses beyond that first calculus class, much of which I was reminded that we'd never use any of the formulas in future courses anyway. This made it feel like I was wasting my time, and nothing kills interest faster than that.