Since the OP didn't share what the Australian school year looks like, I wanted to compare. Here is what I found (all numbers are presuming public/state schools...I assume that like in the US, private schools can and do have different calendars)

"The school year in Australia goes from late January until mid-December. It is divided into two half-year periods (semesters) with two terms each, the so-called High School Terms. Each term is approximately 10 weeks in duration. At the end of each term there are school holidays."

So, their year runs on the calendar year, with no long break in their winter. Their longest break is after Christmas, which is summer there. It looks like its approximately 5-6 weeks long. They end up with.....about 190-200 instruction days per year. It starts roughly in their early summer through autumn and winter and ends at end of spring.

Typically in the US, 180 is the minimum number of days, and anything over 190 is uncommon. The US school year also starts in summer (although later in the summer), runs through autumn, winter, and spring, and generally ends before the start of the next summer.

My nephew is Belgian (my wife's brother moved to Europe for grad school, met and married a Belgian and as of 2022 became a Belgian citizen), and I lived in Germany. The Belgian school years seem to be similarly aligned with the most the rest of western Europe, AFIAK. His academic year starts Sept 1, and ends on June 30, with a week long break the first week of November, 2 weeks at Christmas, 2 weeks at Easter, a week in February, and a full 8 week summer break starting July 1. I knew these dates because my wife and her brother coordinated when we could visit each other with our kids.

My observation of the dates of German school year as that it started in late August, had a longer Christmas break than my kids in the DoD schools (2 weeks for US kids, 3.5 weeks for the Germans) and they had close to 2 weeks at Easter vs just Monday for the DoD schools, and then usually ended the school year in the first week in July (vs the 2nd week of June for the DoD schools). So....slightly different, but very similar to Belgium, the Netherlands, and France.

I think most of Western Europe has a similar schedule: the longest break is during the warm summer months, a rough total of 180-200 instruction days, a long-ish break at Christmas, and some other smaller breaks thoughout the academic calendar.

So I am not sure what the OP finds confusing about the US calendar, since its not dissimilar Western Europe and other nations in the Northern Hemisphere. The seasons are reversed, but their breaks are still pretty much in line with their respective seasons.