As a european this is simply not true. The number if well paying tech jobs in Europe is miniscule in Europe and they are usually region locked to few cities let alone countries.
US gives you freedom. Europe locks you to a country and culture you don’t necessarily want to live in.
If the big companies have offices in Amsterdam and you're not Dutch, you'll have to move there but basically never be considered a local, even if you learn Dutch.
....and? It's literally true everywhere in the world. I've moved abroad 13 years ago, obtained citizenship of another country, settled here, but I still wouldn't call myself local. Why is that a problem, and why is this in any way shape or form "limiting" in moving across Europe? The truth is you can move to any country any company incredibly easily with an EU citizenship, and yet OP finds it "locking" in some way, and I was curious what they mean, because in my opinion and in my experience it's the exact opposite.
We are comparing US single market vs EU single market. It's EXTREMELY difficult for people not in IT to move across Europe. Many of us have spouses or family in professions which cannot easily be done in different EU countries due to the language limitations. That can easily set you back years in your career or force you to learn a language YOU DO NOT WANT TO LEARN.
Another aspect is local culture. Europe is still INCREDIBLY centered around national cultures despite people trying to be more open.
A lot of X-nationality are still acting according to stereotypes and it's incredibly hard to stay in such country longterm.
Part of being happy is to live in a welcoming, happy place not just money and amazing infrastructure.
I have a life in country A (house, work, wife ..etc). My opportunities are limited to companies having LLC in my country or B2B contracts.
If I were to accept a job in country B I would (in 9/10 scenarios) need to move to that country and adjust to the local culture and language.
I had a friend with korean wife who was in Germany and then Belgium each for couple of years. The whole family was suffering from the constant need of adaptation to local languages and eventually they ended up going to Canada.
US gives you freedom. Europe locks you to a country and culture you don’t necessarily want to live in.