Contempt of court in the U.S. escalates considerably beyond fines if the company doesn't start complying quickly. The court can jail the company's officers, issue an injunction forcing them to stop doing business, instruct customs to blockade them at the U.S. border (in the case of companies selling physical goods), and a range of other things.
That's when it's a US company if it's foreign it will end up on the US trade department sanction list which will blacklist them world wide not only in the US and will prevent any entity which operates in the US from doing any sort of business with them.
There is nothing that a Brazilian judge can do to whatsapp other than to harm them financially cutting off 100m users even in a developing market sends a clear sign.
Facebook has an office in Brazil. I don't really understand why they couldn't just levy financial penalties, since Facebook does actually have a business presence in the country.
WhatsApp and Facebook are still separate legal entities as far as i know, the subpoena was issued to WhatsApp it didn't comply they've issued a court order to block it in order to compel it to comply.
If a US company would not comply to a court order, a US judge can prevent the company from operating at all by freezing all of their assets and halting all of their operations.
You're presuming that that Facebook office in Brazil actually has a lot of assets in Brazil to seize. It's likely that it's a shell organisation and has nothing to seize.