Top money in US is paid by tech companies (FAANGs and similar) who have virtual monopolies on their markets, and thus are printing money. They overpay for programmers to make sure they're not outcompeted on tech and retain their monopoly status.
Second crucial factor is the VC ecosystem unlike anything else in the world. VC-fueled startups (even late-stage ones, like Uber) will also often pay way above market for programmers, because they believe programming talent is the way for the startup to dominate the competition and become a money-printing monopoly.
Europe and rest of the world does not have anything like that. There's no serious software industry (aka "tech") there, neither large and estabilished nor VC-fueled. Programmers are seen as a commodity and not a source of competitive advantage. And, even if there are exceptions, they're not common enough to start bidding wars for top talent which in the US elevated the salaries of top ICs to $300k-$400k.
I think it's even more complicated than that. If you compare salaries for physicians (doctors) or lawyers there will be a huge gap as well. Even though there is no VC-funding, economy of scale or monopolies to speak of.
On the supply side of high salaries I think the economy of scale actually have some impact by creating a higher "floor". For example I would almost wager that every European country have their own Salesforce company (non-SAP web based CRM from early/mid 00's), but the e.g Latvian alternative never broke out to the wider EU. Whilst Salesforce conquered US and then the globe. This puts upward pressure on the virtual monopolists / VC-fueled companies that don't really exist outside the US. Imagine if almost every single B2B software company in the US spent their first 5 years only operating within a single state, and many never expanding outside.
But I think the "demand side" is even more important. Most European countries have lower take-home salaries for large parts of the salary spectra, definitely the top quartile. The reason for that are also numerous. But we generally have high taxes on an individual level, high payroll taxes, high VAT etc. In exchange for that we have large welfare states with larger redistributions both across individuals and across time for the same individual (paid parental leave, pension etc).
Top money in US is paid by tech companies (FAANGs and similar) who have virtual monopolies on their markets, and thus are printing money. They overpay for programmers to make sure they're not outcompeted on tech and retain their monopoly status.
Second crucial factor is the VC ecosystem unlike anything else in the world. VC-fueled startups (even late-stage ones, like Uber) will also often pay way above market for programmers, because they believe programming talent is the way for the startup to dominate the competition and become a money-printing monopoly.
Europe and rest of the world does not have anything like that. There's no serious software industry (aka "tech") there, neither large and estabilished nor VC-fueled. Programmers are seen as a commodity and not a source of competitive advantage. And, even if there are exceptions, they're not common enough to start bidding wars for top talent which in the US elevated the salaries of top ICs to $300k-$400k.