United Airlines has Los Angeles LAX to Buenos Aires EZE at $469 round trip for travel in March to May and ticket prices in $500s for several other months. American Airlines has Houston to Buenos Aires at $469 round trip with travel dates from March to November. Copa Airlines has San Francisco to Buenos Aires at $457 round trip for travel from March to November.
Buenos Aires has not rarely been on sale for the past year from California cities. I do not recall posting a Buenos Aires low fare for more than a year.
There are also low fares in low-$300s to Lima.
United Airlines Los Angeles LAX – Houston IAH – Buenos Aires EZE – IAH – LAX