why such approaches are not tried in the US

It depends on how you define Internet access... if you are talking greater than 1.5 Mb/s then there are large parts of the US without that. And you might actually get better coverage in some cities in Brazil because they have 4G networks (or some equivalent). My guess is that the maddog network would be about putting dishes on top of buildings and doing networking that way as its easier than digging up roads etc. [Though it depends on the city and area of city in Brazil.]