Brazil has a weird policy (the "reciprocity" law) that makes them apply to visitors from some countries whatever that country applies to visitors from Brazil. In theory that only applies to what kind of visas are necessary, but often they do so in terms of immigration/customs policy too.
So yeah, a while ago the US started requiring electronic fingerprints from Brazilian visitors (and everyone else I think?) so that's why Brazil started requiring that from US visitors.
I am Brazilian, and I think it's an outdated measure that serves little to no benefit, especially for Brazil itself.
It's fun (in a semi-vengeful way) to submit, say, Americans to the same level of scrutiny they apply to Brazilians. But it also means you're creating artificial barriers against making the country a more popular tourism destination. People in some countries are just not used to having to go throw all these hops to get to visit a country, just because they don't have to; when they learn that they have to go to a consulate in person, in select cities, stand in line for hours, go through an interview, and pay about $150 or so for the right to visit the country, they're quick to change their mind and just pick some other destination that is either easier or that allows you to do all of that online.
The country is basically making it difficult for people to bring you money.
This policy hurts Brazil more than it hurts anyone else.
It does make sense to do this, more countries need to stand up and say if you treat our citizens this way we are going treat yours the same. I mean the travelers interact with border control and the citizens are the only ones who legitimately can bring these complains to their border agencies. Ultimately it comes to be that citizens need to defend non-citizens rights and "reciprocity" policy might be effective because most people only act on their selfish interests.
This policy has been in place for decades with no change. That makes me doubt it effectiveness. I've heard of plenty of USA -> BR travelers being turned away at the border because they didn't realize they needed visas (a common occurrence for people traveling for conferences). Ultimately they understand the reasons and even empathize with the country, but it doesn't change the fact that for them it's easier to just not come.
To me it's more about an ineffective, vain attempt to show power than anything else.
So yeah, a while ago the US started requiring electronic fingerprints from Brazilian visitors (and everyone else I think?) so that's why Brazil started requiring that from US visitors.