Unlike other groups, the Mapuche survived the first wave of European colonialism in the XVI century. There are many factors in this, but I personaly wouldn't underman the roll one man played in this:
Lautaro.
From 1550 to 1860, the Mapuche were not only able to keep the Spanish at bay, but were able to expand east accross the Andes. By 1800, Mapundungum was spoken from the Southernmost part of Patagonia to Central Argentina, and from the Paciffic coast of Chile to the western limits of the province of Buenos Aires. The Mapuche adopted European crops (wheat, apples) and animals (horses, sheep), in the same way thay had previously adopted incan techniques (silver metalurgy) and animals (llamas, in Central Chile).
Yet they keept organized in tribes, and their agrigulture was never as intensive as Spanish or Andean agriculture had been. This meant their numbers, at least in the Pampas (where they had assimilated local tribes), where never bigger than tens of thousands.
They never produced guns, for example, nor did they have proper cities.
This meant they weren't able to stand the second age of European Imperialism, in the late XIX century. Thechnically, they were attacked by Agentina and Chile, not by European states. But the effect was the same, and it was all part of the same process, that saw the Natieve North Americans in the West, the Zulu in Africa, the maori in New Zealand and the Tuareg in the Sahel defeated by culturaly Western countries. Mapuche couldn't beat armies armed with Remigntons rifels, nor could they outnumber the population both Argentina and Chile have (Argentina was slightly populated, but even so it was much largers in terms of population than the Mapuche, and was in condition to draw in millions from overseas.
In short, unless the Mapuche are able to arganize a proper State between 1600 and 1850, with intensive agriculture, cities and large population, and are able to produce their own guns*, they won't be able to survive the XIX century, unless an European power like France establishes a protectorate and commits a lot of funds, weapons and men to their protection.
*
the problem is that, if they build such a state, the Spanish in Chile may redouble their effors to conquer them, since they'd be wealthier.