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

No

The difference between Brazilian Portuguese and Continental Portuguese regarding the word "assistimos" lies in grammar and typical usage (specifically, regência verbal or verb government).

When using the verb assistir with the meaning "to watch," Brazilians frequently use it as a transitive direct verb, meaning they omit the preposition "a" (e.g., assistimos o filme). In Portugal, the verb is strictly used as a transitive indirect verb, meaning the preposition "a" is mandatory (e.g., assistimos ao filme). While both forms are understood in both countries, the omission of the preposition is a hallmark of Brazilian speech, whereas its use is a standard requirement in Portugal.

Brazilian Portuguese Examples

1. Assistimos o filme ontem à noite. (We watched the movie last night.)
2. Assistimos o jogo de futebol no estádio. (We watched the football match at the stadium.)
3. Assistimos o desenho animado com as crianças. (We watched the cartoon with the children.)
4. Assistimos o telejornal agora pouco. (We watched the news report a short while ago.)
5. Assistimos o documentário na escola. (We watched the documentary at school.)

Continental Portuguese Examples

1. Assistimos ao filme ontem à noite. (We watched the movie last night.)
2. Assistimos ao jogo de futebol no estádio. (We watched the football match at the stadium.)
3. Assistimos à animação com as crianças. (We watched the animation with the children.)
4. Assistimos ao telejornal há pouco. (We watched the news report a short while ago.)
5. Assistimos ao documentário na escola. (We watched the documentary at school.)