“In real terms, American wages have been declining since 1969. Immigration has played a major role in the decline.”
Not really. What happened was WWII destroyed the rest of the developed world leaving the Americas mostly unscathed.
Argentina and the US had similar standards of living at the time.
Gradually, the advantage of not having a war fought inside your borders has been gradually wearing off.
This is the reason for the decline of US wages is the rest of the world is rebuiding and the US is declining naturally, the same as Argentina.