Do Americans need a visa to go to Brazil?

Yes, Brazil is not among the visa-free countries in the United States 165.

Visa-free system:

The visa-free policy for foreigners in transit is a part of the visa-free system implemented in all countries of the world. It refers to the policy that foreigners transit from one country to a third country without applying for a transit country visa and can stay in the transit country for a short time according to the laws or relevant regulations of the transit country. China implements a 24-hour transit visa-free system, which is limited to airport ports. Shanghai provides a 48-hour transit visa-free policy for passengers from some countries to transfer between airports and ports.