Culture.

Look at how countries are clustered on this map:

South Americans just do not have the culture of narcissism ("self-expression") and loathing for traditions that defines modern Western Culture ("Protestant Europe" and "English-Speaking" on that chart).

The average USA citizen doesn't really belong in that cluster either - see chart - hence the burning paranoia among Western elites that the USA might "defect" from the West if it found a strong, populist leader.