The general Brazilian vision about Americans is that they are in majority, exceptionally educated, and America, the perfect country, with happy families, no political or socio-economical issues. The Brazilians that lives in Brazil and not had the opportunity to visit the U.S. to face up the real true, see the American population excessively patriotic and self centered to a point of arrogance.
Of course, there are many other stereotypes believed here, but among the most popular, are the Americans as white people that lives well and have everything in their homes, from a nice tennis shoes to the most modern computer or mobile device. The upper and middle classes think that Americans walks on water. They will treat the Americans like royalty and everybody will want to practice their English with you. By the other hand, the majority of the Brazilians from the lower classes don’t care where you came from, so long as you speak Portuguese.
Most Brazilians do not speak English or won’t be able to have a conversation with an American, so for them even the internet will not help much. Brazil is also a nation of immigrants and it is easy for people of any ethnicity to pass for Brazilian, so assimilation happens rather quickly. Europeans are better liked because the language helps a lot. Italians get along exceedingly well as the patterns of behavior are similar. Portuguese are, for the most part, treated as locals. Spaniards assimilate pretty quickly as well.
There is a kind of anti-American sentiment in Brazil, but it is based on facts about how the U.S. conducts its foreign policy, in particular in regards to South America. Again, it’s important to know that Brazilians dislike the U.S. and its foreign policy, not the Americans themselves. Politics by side, Americans are very welcome in Brazil and Brazilians knowing you are an American, will try to be your friend and will get as much information as possible about how is living in the U.S. The “American Dream” is still live for a good part of the Brazilian population.