Why does then EU countries have much cheaper and faster internet and cell data than the US? The market there has much more regulations with one explicit goal being to increase competition.
At least as to wired Internet, they don't: https://www.akamai.com/fr/fr/multimedia/documents/state-of-t...; see also: https://www.recode.net/2017/12/13/16773062/global-internet-s.... The U.S. beats Germany, the U.K., France, Spain, and Italy (the countries comprising the large majority of the EU population).
The U.S. is also one of just five countries to have more than 90% LTE coverage: https://opensignal.com/reports/2018/02/state-of-lte. The big EU countries have faster LTE speeds, but much lower coverage (ranging from 65% in Germany to 83% in Spain).
Belgium has a 94.5% coverage as per last year. The report shows 85%.
The reason is pretty simple, per the report: "OpenSignal's availability metric tracks the proportion of time users have access to a particular network."
That's not coverage. Your source doesn't show what you think it does!