> On one hand, this isn't true.
Ask the native Americans whether or not this isn't true.
> Not at all, I want to iterate on the culture that produced the United States
That culture is built on violence, slavery, racism and oppression. Iterating on it seems to have brought out its worst elements rather than its best elements. Half the country, including you, voted for a caricature of what a decent human being should be like as president. And you are now 200 days into an assault on your economy and freedoms and you still refuse to see what the end game looks like. That culture? The 1950's are not coming back. And that's not a bad thing.
> Our H1B cap is just 65,000 people.
That's just one form of immigration, why stop there? What about refugees? Oh, right, the USA is good at waging war but then ignores the refugees that inevitably are created, that's for the rest of the world. Handy, being a continent sized country an ocean away.
> If you spread them around the country, we could maintain an economic edge while minimizing foreign influence.
Foreign influence is minimized by limiting the use of money in politics which is an easy avenue into the heart of the political system. Immigrants - as a rule - do not have the vote.
> High-skill immigrants who came to the U.S. pre-H1B, and ended up by the handful in small town america here there was a nuclear research lab or whatever ended up highly assimilated.
Small town America is a lot more racist than you think. They didn't so much end up assimilated, they ended up scared to go out of their houses. If you think you are assimilated and that small town America is accepting and nice you should try to live in the places with < 10,000 inhabitants where the White Master Race is the dominant majority. You'll see - very quickly - how they look at you.
Your USA experience is for the most part informed by living in the larger cities. I've spent a lot of time in rural America (~ a year in total) , easy for me to do since I'm white. What people say in private is hair raising, and really opened my eyes to how deeply embedded racism is in the United States.
> do you really believe that the result of these changes will make American culture more orderly, efficient, functional, and democratic than say Massachusetts in 1950?
I don't know about that. But I also don't think that the current political mainstream in the United States cares about orderly, efficient, functional, and democratic elements of the USA unless it benefits the 'in-group' to the exclusion of everybody else.
This whole discussion reminds me of a guy sitting on a branch cutting the live side with a saw while sitting on the dead side. All of those elements that you wish for have been put in place against massive pressure from the people that you support. And they'd love to go back to Massachusetts, 1950. But without you, and your kids. Your wife is - probably - safe. But you can bet that ICE showing up at your door - or your parents, for that matter - at 4 am is going to be very bad news. And they won't care who you voted for either.
As for that 'Dutch Experiment': it isn't limited to the Netherlands, and by and large the Surinam immigrants have disappeared into background noise on account of their relatively low numbers. But when they first came here (just before Surinam became independent) there was a lot of outcry about this. Now, so many years later there is still a fairly large number of people that identify as such here, most of them live in the three big cities, because of small town racism.
The predominantly Turkish and Moroccan immigrants have set up their own regional presence, some of them have held very strongly to their original identity and stepping into their homes is like stepping into a time/space displacement machine. But they - as a rule - are friendly, incredibly hard working and because they value family a lot more than the original inhabitants and their offspring tend to do, have a fantastic social network around them. Again, due to racism and very overt discrimination their kids have - for some fraction anyway - grown up frustrated. They see all this wealth around them and the skin color based ceiling is so strong that only very few of them manage to break through. The end result of this is that a fraction of them rather than being 'kept in their place' by the whites here - who think these people will never be successful and who deserve to work in crap jobs no matter how intelligent or capable they are. It will take many generations until this has reduced, but there is some - very slow - progress over time. I see more and more people with such backgrounds in positions of influence and some power and wealth and they are the beacons that the next generation will hopefully set course by. It will take many more decades until they are no longer pushed down as a group, and, unfortunately, they are not usually helping and neither are their parents. Intermarriage is rare, which would be one way to reduce the barriers between the various groups.
Romanians, Poles and other people from Eastern Europe have moved here in fairly large numbers. As a rule they are doing fine, even though the newspapers love to magnify the few cases where they are involved in legal or traffic issues.
Syrians and other refugees have not integrated well at all. They have been here only a very short time and are slowly displacing the older immigrant groups for the lowest income jobs. I've had very little interaction with them. But the various asylum seeker places that are dotted across the country are best compared with open air prisons where our bureaucratic engine driven by overt hatred tries to discourage them from staying here. There are far better ways of dealing with this but unfortunately my vote is only just as heavy as that of the racists. It will be decades more before these people too have made this place our home.
Ukrainians, who are here in surprisingly large numbers have integrated in record time. They have learned the language and have assimilated very quickly, to the point that you have to have an ear for it to spot them. They are everywhere and they seem to love it here. It helps that their culture and ours was already closely parallel, besides the Orthodox Church component which quite a few still formally subscribe to (religion, in NL, was on the way out until immigrants brought it back).