Is there a car rental company (i.e. Hertz, Budget) that redeem US earned points in central/south america?

Different companies are present in different countries, your best bet is to narrow your search some, check a particular destination and check the company. Google say..." Buenos Aires / Hertz" and you can figure out who is where.

Be mindful, rental vehicles are MUCH more expensive in SA than in the US and driving locally can be a challenge. You have to be mindful of others as you would be driving in a very large city. Safety is also an issue to consider, depending on the destination. Do NOT skip on insurance. Ever, for any reason. under any circumstance.

Check each country to see what requisites exist for foreigners and drivers.

Make sure you have a working local cell phone and have emergency/ rental/ insurance roadside assistance number handy.

Use clean underwear.

If you have frequent flyer miles (or any type of points), go to that company's web site and look for their "partners". Most airlines partner with rental car companies and hotels.