Correct if I'm wrong but at the time didn't Spain hold parts of Italy, France, the lowlands and Portugal. If they wanted to they could send people. Not to mention the hordes of Germans that are willing to go to the new world if given the chance.
It's missing the most important part: settlers.
Spain didn't have the manpower to send to all the different colonies.
Plus, you need the modernization to make Wheat profitable.
Agricultural colonies (ie settler) require an excess of populace. Spain never had that problem.
the La Plata region has the pampas. other than that, not really anything needed to make a country. the lower, more inhospitable regions, have minerals, but they're not easy to get to for a long while.
The main problem is the prevailing economic conception which regarded the lands of the future Viceroyalty of Rio de la Plata, as land worthless for lack of gold and silver. It should be noted that the initial exploration occurred to try to find a waterway that connected with Peru and attempt only to fail the formal settlement of the region began.
The assessment of the region is only beginning to be introduced and begin to increase livestock production.
But its main product the 'Charqui' (jerked meat or jerked beef) this was a term from Quechua origin. this type of dried salted meat was unfit for export ... what if it had value, were the hides of cattle to the point that often sacrificed animals for their hides and only after consuming some cuts of meat selected, at the time, it is used to squander the rest of slaughtered animals.
This type of economy that suited the vast plains of the region populated by wild and hostile native tribes with very little European presence stable outside major population centers and that also did not require much labor and required greater financial resources or deploy important military forces permanently to ensure its continued operation, in this kind of economy suited to scarce resources to this border region and limited colonization compared to Peru.
This situation was all the result of specific policies that favored regions with abundant indigenous labor required for mineral resources exploitation and so
and by the shortage of financial and human resources to devote to regions as unprofitable for the crown and the economy of the time, as were those of the Río de la Plata, initially as colonial polity.
This situation in no vario even after establishing himself as the intermediary trade with Peru ... except for its proximity and its commercial intermediary function later would give strategic importance to
the Río de la Plata.
It does not conceive at the time, another possible type of economy for the region ... at least initially at the time of colonization. Agriculture being practiced only in the vicinity of the towns and villages and limited to subsistence and / or to the production of small surplus for sale.
**During the rest of the colonial period and part of the independence period, such
*based on the exploitation of cattle economy, it was unquestioned in the inner regions of the Río de la Plata.
With regard to the population under Habsburg rule that theoretically could have been available as a source of potential settlers to the American dominions of Spain... it could have been if the policy of colonization and trade of Spain and the Castilians in particular had not been so exclusivist and had not limited with hundreds of regulations and laws, trade and immigration to and from America.
Which they were created and maintained, besides to exclude non-Spaniards and as a way of selection of those who would be allowed to immigrate to America.
For the aforementioned economic, social, political and psychological reasons a change of mindset is required in the Castilians counselors of the first Habsburg monarch, to be allowed in the future to at least some of the subjects other Hapsburg monarchs, to immigrate to America.
The unique exceptions were the land grants in New Granada that the Emperor Charles V gave his bankers... which were motivated by his great indebtedness to them. These concessions were an economic and political failure besides that besides ruin them, depopulated and ruined the regions covered by the concessions.
Among other reasons, as stated in all the chronicles of the time, due to the rapacious and ruthless actions (even by the standards of the time) to his need to recover by the rapid exploitation of land granted loans owed by the Spanish monarch.
Another consequence is that reaffirmed the exclusivist immigration policy regarding America.
After the above still it requires the cultivation of land in general and in the regions of Rio de la Plata in particular as a proxy activity profitable and invest the necessary resources to initiate and sustain could be recovered.