If by North American, you mean United States, then I think the answer is yes, it probably is easier than the UK but….
Firstly, the UK A level system is intended as preparation for a 3 year university degree. In the US, full degrees are 4 years – so one could argue that high school is intended to finish one year earlier and that the first year of a US degree is very roughly equivalent to the final year at high school in the UK. Also, I think that in the US, a higher proportion of students complete high school than complete A levels in the UK. (Around 90% of 25 year olds have completed high school in the US. Not sure what proportion of A levels or equivalent in the UK.) So I think that completing high school in the US is intended to cover a wider range of students.
Secondly the US system is very flexible and much less standardised. So one could finish high school with a very low level of academic rigour – or one could have taken many tough courses. In addition, students will have taken a much wider variety of courses in their final two years of high school than is the case in the UK, which is focused on three (or maybe four!) A levels. This flexibility continues at the degree level. With some exceptions, one does not usually apply for a particular course of study. Rather you state your intended major but are not bound to that. You end up “declaring” your major sometime during your first or even in your second year. (I know of someone who started off as a finance major, then switched to medicine and finally settled on Latin. I think there were a couple more in between that I’ve forgotten about.)
The US high school system is also much more about “continuous assessment” than a final set of A-level style exams upon which your final score is almost entirely dependent. This means you get marks for homework, assignments, quizzes, tests, etc, etc. with end of term exams counting relatively little. Your subject total mark counts towards your overall GPA (grade point average) and this is the single most important factor when applying for college in the US. The problem is that every high school has a different way of calculating GPA’s, although universities will usually adjust for this.
When applying for college (meaning university!) in the US, the admissions are very interested in your grades from Grade 9 to Grade 12. In fact your final year Grade 12 marks may count for very little! This is because one applies for college towards the beginning of twelfth grade (before having much in the way of grades for that year) and may have been accepted before the end of the first semester. The student is expected to maintain the kind of marks they had achieved when applying but unless they really bomb out, they are unlikely to be rejected. Hence a lot of twelfth graders suffer badly from “senioritis” in the final semester.
The US does have standardised test. Most college applicants will take either the SAT or ACT (they are run by two different organisations but are very similar), which are mostly multiple choice style tests focussing on maths, English and “reasoning skills”. They don’t require a particular advanced level of either (I’d guess the maths level is around GCSE level?) but can ask some quite tricky questions based on that core knowledge. One will submit SAT/ACT scores when applying for college, although some colleges are “SAT/ACT optional’ meaning they don’t require you to submit a score. There are also SAT/ACT subject tests but far fewer universities require these, although many of the better ones do, especially for the STEM subjects.
In addition, the US also has “AP” (Advance Placement) courses. These are like normal subjects (in that there is the usual “continuous” assessment from your school) but there is also a standardised final exam (i.e. everyone writes the same exam at the end). In the exam, you get a score from 1 to 5. So you could get a very good continuous assessment mark but still do badly in the final exam – or vice versa. Many universities offer credit if you get a 5 (or sometimes 4 or 5) for the equivalent first year subject. Getting enough AP credits, could mean graduating a year earlier. However, AP’s are also not equivalent to A levels. A strong, but by no means exceptional, student might take 8 AP’s over the last two or three years of high school, in addition to non-AP courses. In addition, some high schools may offer courses “beyond” the AP level.
AP scores count for almost nothing when applying to US colleges but are the most important thing for US students who apply for UK undergraduate degrees. There are probably a couple of reasons why they are not much considered in the US. Firstly, the number of AP subjects offered by high schools differs enormously – many high schools, especially in poorer areas may not offer them at all. So it’s regarded as somewhat unfair to hold it against students who didn’t have the chance to take AP courses. Secondly, although you can take AP courses in any grade, students will typically take the most in their final year, so those results won’t be known before applying to college. (And remember that most colleges give “unconditional” acceptances long before the end of 12th grade.)
So, is the US system easier? It certainly can be but for students taking a rigorous set of courses, I’d say it’s much more debatable. The US system is less focussed but covers a wider scope.