So they can rob noncitizens using asset forfeiture laws. Never travel in or through the US if you need to transport large sums of money or valuables.

Actually, the better advice is never travel in or through the US. I wish that were an option for me.

A couple of times I've travelled Air NZ route that goes London-Auckland via LAX. The plane has to stop to refuel I guess. All the passengers are forced to queue up to be fingerprinted and have their eyeballs scanned, while a security guard walks up and down screaming "STAY IN THE LINE!" Then they're herded into a lounge barely big enough to hold everyone (first class passengers have their own little pen next to the toilets). Apologetic air crew distribute apples, crisps and bottles of water. For hours. Through a glass wall is a view of the rest of the airport: shops, cafes, bars, space to stroll. But hey, at least you get to not miss your flight, and the US is safe from Kiwi tourists.

I don't know if they still do this, I avoid the route.

Because fuck you, that's why.

Also, freedoms or something, I dunno.

I only stopped there for transit on a flight to Mexico. Just before boarding my flight I was told that I need a visa for the US, which is extremely weird because normally airports have transit zones where you don’t need any visa. But apparently the US is special, so you actually have to enter the country before going right back into the airport. This nonsense made me miss my flight.

Not like that, they didn’t let me board my flight from Europe to Texas. Even though I had a connecting flight to Mexico few hours later.

I am no longer on your side. if your journey is :

European country X -> Somewhere in the US -> Texas -> Mexico

Then of course you're going through security controls, etc etc. You're going from the international processing and flights part of the airport to the domestic flights part of the airport, which is the zone where any asshole in that country can travel in, so you're properly entering the US. Of course you need proper clearance and visas and all that.

I initially assumed your journey was

Non US country-> Somewhere in the US -> Mexico

which you'd be completely right