Easy answer, but it requires understanding what wins games at the full national team level. It requires the best, most powerful athletes who also happen to have sufficient technical ability and vision. Players who have the best technical ability and vision, but are lesser athletes, are always a losing recipe at the highest level on the women's side. For example, compare Jessie Fleming to Julie Ertz. Fleming has incredible technical ability and vision, but she is nothing compared to a beast athlete like Ertz, despite all of Ertz's technical flaws and lack of finesse. Ertz is much bigger, stronger and faster than Fleming, and no amount of practice will ever bridge that gap. It's why Rose Lavelle is great against most teams but was a non-factor against France, the only other team that can remotely compete from top to bottom athletically to the U.S.
When US Soccer selects youth players, it knows what it's doing. It almost always selects the best, most powerful athletes because it's looking for 1-2 per age group whom it will ultimately need for the full NT that also have sufficient soccer ability. Sure, it sprinkles in some technical players who aren't quite as athletic both because there are only so many uber athletes in an age group and also because they help teach the horses it actually cares about. But it does not select players based on which combination is likely to win youth tournaments, because winning youth tournaments does not matter. It does not select the best 11 circus jugglers who lack elite-level athleticism because those kids are a waste of time at the highest level, even if they may be the most likely to help win U17 games. It is perfectly fine that any opponent has the 3rd-11th best players in the game so long as the U.S. has 1 and 2. And as long as it has the 11 best athletes on the field in an age group, it almost always will have the 2 best overall players, because superior athleticism is relatively more important than superior ball skill.
Also, countries with players who train together all the time have a huge advantage over the US at the youth level. Many other countries are able to have their kids train together far more often because it is almost always easier geographically, and also because their systems tend to be more centralized. Of course, the centralized structure is also often a result of geography. In the Netherlands, for example, every single kid can be at a central location in about 2 hours. In China (back when they cared about women's soccer), they can just make every child in the country move to one place. But it's stupid to try to convince a critical mass of elite U.S. girls to all move to one part of the country and attend the same soccer school. And because it takes 8 hours and a lot of money to get a kid in CA to the U18 national camp in FL, you just can't hold camps very often. In short, when you put 11 technically great foreign youth players who train together all the time up against 11 beast athletes who get together briefly every once in a while but have no idea how to play well together, the former are going to win more often than not. But the latter ends up having the two kids on the pitch, and that's important because those are the only ones who matter, and there will be plenty of time to incorporate them into the full NT once US Soccer figures out who they are.
And, in every country but the U.S., it's usually a really stupid idea for a girl over 18 to waste time playing soccer, so very few do it. But it's a great idea for thousands in the U.S. because it's often a condition of their scholarship. Which means the U.S. has a massive pool of adult players to choose from, while many countries realistically only have 30-40 in an entire country.