There's absolutely nothing special in this case because WhatsApp happens to be operating on the internet. Suppose they were a mail order company based in Brazil but serving customers internationally by post. If a US judge issued a court order in the US requiring the company to hand over business records stored on paper in Barzil, he would have no jurisdiction whatsoever. Brazilian law protecting the privacy of information stored in Brazil would prevail. there would be no controversy about this.

The fact that WhatsApp's info is stored on servers rather than paper records is irrelevant. The jurisdiction in which the records reside applies. Although the fact that their servers don't even store the information requested anyway should be.