Unlike the Spanish colonies Brazil was administered as a single colony with one single government for almost its entire existence, it began as separate private colonies then was unified as single royal colony, split for a few years between north and south and then again reunited for more than 2 centuries.

Besides this, before and after independence there were separatist movements but they were quickly defeated with the exception of Revolta Farroupilha, a separatist movement from the southern most province that still has supporters today much like in Texas. This war lasted for 10 years and for a time it looked like they could win.

If this revolt and other were successful Brazil could be at least 6-7 countries.

And there was one successful independence. The Cisplastina province (Uruguay), though settled by the Spanish was part of Brazil and only gained its independence after Brazil's own independence from Portugal.