Take a look at the "daily new deaths" graphs for each of those countries on the site you linked. All four of those countries fall to near zero over the summer. Their first-wave lockdowns worked, eventually. The USA's did not; people just kept getting infected all summer long.

The second wave has hit hard, but deaths in Slovenia, Belgium, and Italy are at this point all trending back downward. USA's are not. Extend those graphs out and we'll be well ahead in deaths before long. The UK isn't trending down either, but their leadership is suffering from a lot of the same problems as the USA's with not taking this seriously.

Also note that all four of those countries are reporting fewer infections than the USA - their deaths per capita come from higher case fatality rates. This suggests that the death rate has more to do with their hospital systems being worse-positioned to handle the influx of patients than how the spread was managed.