Cultures are different in many aspects. Some cultures are strict about punctuality while others are more relaxed about it. In some countries it is hard to develop friendship while in others people are more open to build relationships. The same happens with humour. A joke that Americans find funny might be viewed as offensive or impolite to Brazilian people and vice versa. Humour in the United States tends to be rather sarcastic. Celebrities and politicians are constant victims of an ironic and sharp sense of humour that is spread by radio and television shows. It is interesting to see how Americans are comfortable enough to make fun of congressman or even the president and yet maintain the respect necessary to their public functions. Brazilians tend to be very sarcastic as well and humour there can very often be inappropriate.
In spite of this similarity, Americans created a genre of humour that is not familiar to Brazilians. TV sitcoms portray funny daily situations that happens to a certain group of people. This kind of show was spread around the world and inspired Brazilians to produce their own sitcoms. However, the success of this genre in America was not the same in Brazil. Sitcoms were unfamiliar to the Brazilians, they viewed it as artificial and not many of them became big hits.
All things considered, it is fair to say that Brazilian humour tends to be more ironic and sarcastic than American humour, sometimes even a bit exaggerated. Americans on the other hand seem to have a better grasp on humour when portraying the daily situations that can happen to specific groups of people in a natural way. Overall, they have a similar taste when it comes to humour and the same joke can be sidesplitting to Americans and to Brazilians.