I think that MLS salaries that these youngsters are better than what they would make in the European second divisions. That might explain why they stay home. Sure, for top prospects, this doesn't apply even though, would you stay home and make money or go to a top Academy with a long shot chance at making the first team? I mean, it might not only be scouting, also willingness to move.
I remember some time ago I looked at MLS salaries and I was shocked how low they are when you remove the "superstars". As far as I can see Reynolds was on USD 70k in 2019. Even a Norwegian club could match that for a solid talent (obviously a Norwegian club would never be able to find that talent - and spend that "much" on someone unknown to the club - but they could afford it).
Ola Kamara who I know well makes 260k. I'm not sure these days, but a lot of players made 260k in Norway some years ago. Since then I believe salaries have dropped, but if he had been younger and had some re-sale value he could have made 260k in Norway.
I believe salaries are higher in Sweden - and certainly for some teams in Denmark.
It's probably a bigger step to move for an American, but it really shouldn't be. We got Norwegian kids moving to Belgium, Portugal, Italy etc. and I would say that is probably a bigger move culturally and language wise compared to an American moving to a place like Denmark.
I know in Norway a lot of the "scouting" is based on a handful of "schools" in Africa linked to probably a handful of agents. Probably easier to go scattergun there than it would be for example with American players.
My guess is that there is some untapped potential there. If decent sized teams from Denmark, Belgium etc. established some contacts and built a network in the US there got to be players that would have loved to get their "footballing education" in Europe.