I'm making major changes to the scenario that I've had for the past several years regarding a British victory in Buenos Aires in 1806-07. As part of this, I want to make a comment in response to a
thread on that subject from 2008-09. I feel that the British would have probably succeeded in Cordoba a year or two after the British take over Buenos Aires and Montevideo, as long as they kept up the pressure on the local Spanish inhabitants of those parts of the Viceroyalty of the Rio de la Plata. That would have caused the Spanish population to eventually resign to being ruled by the British.
Put it this way: Just before the British were victorious over the French in Quebec City in 1759, the French population was not welcoming of the British at first, and the French fought hard against the British. When the British won at Quebec, the French kept up their resistance for a bit (even winning over the British the following year near Quebec City) but slowly but surely, they backed down their resistance to the British. When British soldiers were approaching Montreal in 1760, the French (facing certain defeat) felt they had no choice but to surrender right away. In both Quebec City and Montreal, the French and British agreed to articles of capitulation that would grant the French population freedom of religion and things like that. And I'm not sure if this is correct, but after the conquest of Quebec City, the capital of New France moved to Montreal, but that was before the capitulation in Montreal.
So too, in Buenos Aires and elsewhere in the Rio de la Plata, the Spanish-speaking people would have generally loosened their resistance to British rule as the British would keep up the pressure there. The capital of the Viceroyalty of La Plata would have moved to Cordoba after a British conquest of Buenos Aires. It seems to me that there would have been some action between British and Spanish/criollo troops on the way to Cordoba or near Cordoba. There would have been determined resistance on the Spanish side for sure, but there also would have been a lot of British pressure. Maybe at first, the area around Cordoba gets taken over by the British, and then eventually Cordoba itself.
Afterwards, to further secure the rest of the Viceroyalty (or what's left of it), the British would move troops northward to Upper Peru and Paraguay. Judging by how the Primera Junta armies did OTL, the British would lose most of Upper Peru but would gain territory up until Salta/Jujuy, and would lose Paraguay. After all this, Cordoba becomes a British colony (for a very short time, a protectorate) due to British interest in settling the empty lands south and east of Cordoba city, while the Cuyo, Tucuman/Santiago del Estero/La Rioja/Catamarca, and Salta/Jujuy all become British protectorates.
Which brings me to a question regarding Paraguay: In this TL, Paraguay is invaded by British troops and remains strongly pro-Spanish/royalist; in one battle between those two groups, the Spanish governor abandons his troops (just like OTL). This alienates many Paraguayans away from wanting to remain in the Spanish Empire, which is crumbling anyway. Unlike OTL, there's no immediate model for independence from Spain brought by troops from Buenos Aires. Meanwhile, Paraguay is geographically isolated from the rest of what remains of the Spanish Empire in South America. It is surrounded by the Portuguese (one enemy) to the north and east, the Chaco (a European no-man's land with hostile Indian tribes) to the west, and the British (yet another enemy) to the south. Having said that, does Paraguay remain part of the Spanish Empire, or becomes a British protectorate for a short time, or becomes independent - or any or all of these?