Switzerland is a diverse society with lots of immigration and it is also a high-trust society

That probably has more to do with who immigrates to Switzerland. I don't now the numbers, but people who immigrate to Switzerland is probably fairly well educated and generally pretty well of.

Denmark is still a fairly high-trust society, not to the level of Switzerland or Japan. We're seeing certain items in supermarkets being locked away or chipped to prevent theft. Now that's not just because of immigrants, Danes steal from the supermarket as well, because prices on many items are increasing rapidly.

The huge majority is from Germany, Italy, France, etc. A lot of it is highly vetted, professional migration.

If it adds enough of illegal immigrattion or low-grade legal one, it wont be a high trust society anymore.

Switzerland is so small, basically a city.

That's irrelevant to how the world works.

There are countries that are equal or much smaller than Switzerland with 10x worse crime and low trust. Just look at Jamaica.

And there are countries 12x bigger than Switzerland (like Japan) with high trust and low crime.

Switzerland's population would make it one of the biggest cities in the world, more than double the population of Los Angeles, and more than New York City. Neither of which could be counted as high trust.

The population of Switzerland is ~9 million. The population of LA metro is around 15 million, and NYC metro aroound 20 million

LA "the city" might be less but you can't tell where LA ends and it's other parts begin. It's one giant metropolis. Same with NYC.

The city of LA is just there for administrative purposes. People who live in "Burbank" or "Pasadena" are seen as living in "Los Angeles" by most people outside the region.

You can tell where the city ends very easily. There are well-defined boundaries. Government statistics take that into account. Here's the census page for the city of Los Angeles, which lists a population just under 4 million: https://data.census.gov/profile/Los_Angeles_city,_California...