Brazilian here. I wasn't aware of this thing until I saw this thread (to be fair, I'm more aware of USA things than things from within the country where I live).
It's a rarely situation where I completely agree with a "Brazil bans something" headline. It's a right thing to do, IMHO (well, no photo should be used without photographed's consent whatsoever, be them children or adults, but alright, it's indeed a priority to guarantee children's safety, so... maybe we Brazilian adults could wait our turn to have our privacy respected in the future as well?)
There's a slight technicality I should point out, however: there's no way for "ANPD" ("Agência Nacional de Proteção de Dados", or National Data Protection Authority) to check whether Xwitter is complying with such policy. I mean, how could Brazil confirm that Xwitter really stopped using photos from Brazilian children? Technically, Xwitter could say "yeah, Brazil, we're complying, look, here's the checkbox forcefully turned off for every photo containing Brazilian children", while they'd be secretly using mirrored content from their CDNs located within other countries to train their xAI, outside the reaches of Brazilian eyes and jurisdiction... It'd not be surprising, coming from big tech companies who seek profit.
Perhaps if Brazil decided to do this effort alongside with other nations, it'd be way more effective. But Brazil seems to be struggling with diplomatic relationships because of its involvement with BRICS, so the seemingly lonely effort may be a consequence of an isolated diplomacy landscape.
In summary, IMHO, Brazil did the right thing, although through somewhat weak means.