That is an interesting question. I am not sure that Brazil currently in fact has any 3 or 6 month validity issue for US passports currently. It would seem from searching around the web that no one does. There are plenty of sites which list 6 months as their authoritative number HOWEVER every single one of them is either a year old and many scraping information which is 4-10 years old, which in itself was flawed? Why? Well until 2019 US citizens needed to get a visa to travel to Brazil, however Bolsanaro ended that last year, when US citizens received visas they often received 5 or 10 year visas, and quite frankly you could essentially travel to Brazil up until the last day of your passport, as long as you had a valid visa, if fact they would not ISSUE you a visa unless you had at least 6 months left of your passport - so all info is flawed and out of context. So no, it is not so clear........... with different Brazilian missions even having different things posted on their sites. I would note that the Timatic tools that I just tried (slow day) have no issue even when putting in your passport expiration date(s).So I would strongly suggest contacting the Embassy in Washington (not the Consulates) and getting them to confirm. I have a strong feeling that it is 3 months and you would be under the wire.

As for Colombia, AFAIK Colombia has never had a 3 or 6 month rule, whether enforced of not.