Is the word sistema the same in Brazilian and European Portuguese?

No.

While the spelling and core meaning of "sistema" are identical in both Brazilian and Continental Portuguese, the answer is No because there are differences in typical usage and the gramual structures used alongside it.

1. Usage (Collocations): Brazilians typically use the term sistema operacional to refer to a computer operating system, whereas Portuguese people more commonly use sistema operativo.
2. Grammar (Verb Patterns): The way the word interacts with verbs to describe an ongoing state differs. Brazilians use the gerund (está funcionando) to describe a system in operation, while Portuguese people use the "a + infinitive" construction (está a funcionar).
3. Vocabulary (Contextual usage): The words used to describe a malfunction in a system vary. Brazilians often use quebrado (broken) or travou (crashed/stuck), while Portuguese people prefer avariado (malfunctioning/broken) or bloqueou (blocked/frozen).
4. Pronunciation: In Brazil, the vowels are generally more "open" and clearly articulated. In Portugal, vowels (especially unstressed ones) are more "closed" or reduced, often sounding much shorter.

Brazilian Portuguese Examples:

1. O sistema operacional travou. (The operating system crashed.)
2. O sistema está funcionando muito bem. (The system is working very well.)
3. O sistema de ar-condicionado está quebrado. (The air-conditioning system is broken.)
4. Eles estão instalando um novo sistema. (They are installing a new system.)
5. O sistema de organização é muito útil. (The organization system is very useful.)

Portuguese (Portugal) Examples:

1. O sistema operativo bloqueou. (The operating system froze.)
2. O sistema está a funcionar muito bem. (The system is working very well.)
3. O sistema de ar condicionado está avariado. (The air-conditioning system is broken.)
4. Eles estão a instalar um novo sistema. (They are installing a new system.)
5. O sistema de organização é muito útil. (The organization system is very useful.)