We're mostly talking about ladies singles when we're talking about large numbers. In the early 2000s, when the sport's popularity was at its peak and the maximum number of skaters in one group was 18 under the 6.0 system (now 24 under IJS), there were a couple of regions that needed to use qual rounds for intermediate men in a couple of years. But generally the number of boys competing is well below the maximum, and not all skill levels have enough to hold a competition at all in all regions in all years. In pairs and dance the numbers are even lower, and the juvenile age limits are higher.
There are no state championships. The first level of qualifying competition that conveys a meaningful title is Regionals -- there are 9 regions across the country,
Other than that, there are just nonqualifying competitions, which can range in size from a couple dozen skaters at various levels over a few hours to hundreds of skaters requiring five 14-hour days on multiple ice surfaces. But those are just for fun and practice -- they don't count for anything. (At the handful of largest most important events, there might be federation officials monitoring the top skaters under consideration for international assignments, but that's incidental to their main purpose.)
At the higher levels (novice through senior), there are no age limits or divisions in the US -- age is only relevant when it comes to international assignments. There aren't so many skaters at those levels that age divisions are necessary. It's rare for there to be more than 24 junior or senior ladies in any one region -- maybe up to 200 at either of those levels for the whole country in any given year. For novices there might be as many as 50 or so in a larger region, a few hundred across the country, so they have qualifying rounds at the regional championships.
Intermediate level is under-18. There could be over a 100 skaters at that level in a large region (moreso a few years ago before 13-year-olds were allowed to stay in juvenile) -- about a thousand girls across the country. So qualifying rounds are almost always required, except maybe in the smallest region.
Juvenile is now under-14 (used to be under-13 until 2 years ago). Again, the largest regions could have close to 100 entries and only the smallest region might have less than 25 and not need qual rounds.
Teenagers (now over 14) who have passed the juvenile but not the intermediate test cannot compete in qualifying competitions. There's a nonqualifying event called Open Juvenile they can enter. Many who can pass the intermediate test will move up even when they're not competitive at that level, just for the prestige of competing at a qualifying level.
In addition to conveying a regional championship title, the top 4 skaters move on to the next level, i.e., sectionals. And then the top 4 from sectionals move on to nationals.
(*There have been some changes over the years, especially at intermediate and juvenile levels, but I won't go into past details.)
So the juvenile skill level is already divided into skaters over 14 who are not eligible for championships at all, and skaters 13 and under who do compete at the first qualifying level. Only a small percentage will qualify.
Intermediate skill level has an age cutoff, but it includes almost all skaters of high school age. Those who are past high school and not up to novice skill level are probably not looking to win championships.
Regionals take place in October; ages are as of Sept. 1.
Would it make sense to divide the juveniles at regionals into, say, 10 and under, 11-year-olds, 12-year-olds, and 13-year-olds? Or 11 and under vs. 12-13?
To divide the intermediates into, say, 11 and under, 12-13, 14-15, and 16-17?
That would give more medals to more kids. But in the smaller regions, some age groups might have only one or two entries (especially for boys!) -- so then would it make more sense to combine the age groups in those regions?
How many should go on to sectionals, or from sectionals to nationals? Should there be separate national championships for preteen vs. teen intermediates?
On average, the most talented skaters will move up the levels at younger ages, although there will be exceptions and there will be instances when the more mature presentation of older skaters will triumph over greater athleticism of younger talented ones. So should opportunities to advance beyond regionals be focused on the skaters who are most likely to reach the higher levels at all, or on the ones who are currently at their peak at a middle level? Or both? I think there were also age-divided Intermediate A and Intermediate B events at Junior Nationals at some point, but again that wasn't an experiment that the federation decided was worth keeping.
Usually the age divisions at nonqualifying competitions are made only for nonqualifying levels, below juvenile, and the divisions into qualifying rounds at juvenile and above are made randomly (and at regionals they are seeded at intermediate and above).
I do remember one medium-sized nonqual I attended ~15 years ago that divided the intermediates into three groups by age and then took the top three finishers to a final round. The results fell out very predictably:
1st winner of youngest group
2nd winner of middle group
3rd winner of oldest group
4th second finisher from youngest group
5th second finisher from middle group
Yep. The issue is how to put the skill/age divisions across regions when there's not necessarily as many girls in certain regions. I don't have a solution for that yet.
So not only are the needs of different regions in the US different, you can see how they could be even more different within different federations.