I am not Brazilian, as you can see by my name, but am American born and Portuguese naturalized. Having lived in both countries for a total of forty years (twenty and twenty), and being married to a Brazilian, this is a question that often goes through my mind. When we lived in Brasilia, in the seventies and eighties, there was almost zero contact with Portugal. In a city of one million there was one Portuguese restaurant (looking now I found at least seven). I personally never heard Portuguese as spoken in Portugal, never saw a Portuguese movie, watched a Portuguese TV show, or heard a Portuguese musical group. Today I am sure it has changed a little although I think the average Brazilian has no concept of life in Portugal. Even today there are no Portuguese musical groups popular in Brazil and definitely no Portuguese films known by the public.
Most Brazilians, who have any opinion at all, and we are talking about educated people living in cities with access to internet and who read, still consider Portugal to be a rather old-fashioned, traditional, mono-cultural people with an unintelligible way of speaking. Few Brazilian are aware of the state of the art expressways, the advanced telephone and internet system, the gigantic hypermarkets and shopping centers etc. Portugal underwent a radical transformation in the nineties with EU money and left Brazil behind in many ways.
As far as the Portuguese jokes are concerned, my theory is that they are based on the typical Portuguese immigrant who arrived in the fifties and sixties from Tras-os-Montes, who was usually illiterate, had a moustache (often men and women), dressed poorly in sombre colours, often wore tamancos (wooden clogs), had poor personal hygiene, and worked in lowly professions such as itinerant vendor, butcher, barkeeper, or baker. They stood out in Brazil and were often laughed at until soon many of them became quite rich, having saved and saved, often sleeping on boards in their shops. Soon they were the bosses and the natives were their employees.
One aspect of the Portuguese I noticed coming from Brazil was their literal-mindedness and their inability to think outside the box. My first shock was how Brazilian humor fell flat on the listeners. There was little awareness of language play or criticism of the powers that be. There was, and there still is, a reverence for power and those who have a degree. Someone who has finished university is called a Doctor, and not doing so might even cause serious problems for the interlocutor. Even a politician like José Sócrates, indicted for corruption and sitting in a jail cell, is called Sr. Engineer, even though his degree was fraudulently obtained.
A final point to be mentioned to show the cultural differences is the Portuguese negativity. The Portuguese complain a lot, usually doing nothing about it. While a Brazilian will respond to the question "Como vai"? with "Tudo bem" or "Muito bem" a typical Portuguese response is "Vou andando" (lit. I am walking). Common expressions are "É a vida" and "Tem que ser". There is a fatalism reflected in the language. That you do not see in Brazil.