Belgium has a population of only 11.7 Million, a population density of 387 per square kilometer, and a whopping 98.8 percent of the population is Urban.
We have 30 times your population, 1/10th of your population density, and 20% less of our population is Urban.
The United States has 28 Million people, more than twice your entire population, that MOVES every year. Over a million people immigrate into the United States every year, meaning we could literally populate your entire nation in just a decade.
All of that means you cannot simply “send everyone a letter”.
It’s like the old saw “Everything works fine in a small network.” So no offense but relatively speaking Belgium is a tiny network compared to what we’ve got going on in the United States.