In the HN context in particular, it's important to observe that the underlying legal philosophy of monopoly differs in European and US law.
It's not just that the laws are different; it's the goals of the laws. The European laws (in general) attempt to stave off competitor harm. They're historically sourced to guild protections and seek to create a situation in which companies can compete. Small players in the market are seen as inherently a good thing, regardless of whether that actually makes a better market for consumers (which it is not guaranteed to; laws protecting the existence of small book stores keep prices of books artificially high in a world of extremely inexpensive data copying and book fabrication. French book buyers are essentially paying a hidden tax to have corner book shops exist, whether or not they care if corner book shops exist).
The US lacked a similar guild history and, instead, historically experienced the threat of government overreach privileging the existence of incumbent companies over new players. The US therefore has laws crafted to protect against the major threat the US historically experienced: one company making life miserable for consumers (i.e. the Rockefeller threat, or going back further, the British East India Company threat). Neither US law nor US monopoloy philosophy traditionally care whether small-time market players can compete at all ("why should it," runs the argument, "maybe Starbucks is ubiquitous because their coffee is actually better. What's the value to the consumer of propping up bad coffee?").
It feels like 90% of arguments on HN on the topic are unaware of that philosophy gap.