You can fly to Miami with American or Aerolineas and connect from there to WA. You can also fly to NYC with Aerolineas.
You can also fly to Mexico City with AeroMexico (direct) and from there to WA. Or you can fly to Panama City with Copa and then to the US.
Alternatively, you can fly with Aerolineas to Santiago and from there go to the US with LATAM. Might be a good option if you want to use that LATAM ticket, see if you can call and ask if they would reroute you via SCL and you just pay for the flight to Chile. You would need to make the connection the same day as you won't be allowed to enter Chile.
Another alternative is to fly to Sao Paulo (GRU) again with Aerolineas and got the the US from there. GRU has the best number of available connections to the US right now. However, you can only fly from Brazil to the US if you are a US citizen/permanent resident (which I presume you are). Flying from Brazil may also require you to self-isolate at your final destination in the US but that might be the case even flying from Argentina depending on what the local authorities in your state/county are requiring. Note that Brazil accepts tourists so you could enter the country if you need to. You'd need a letter from your health insurance provider (can be auto generated online) that you have an insurance covering you while you are in Brazil. I think even a letter or a print out from a credit card coverage policy might work. Need to do your research. Ain't the easiest option but if you are savvy you can do it. Could then also use that LATAM ticket you have to save $$$.
So, by far the easiest option is flying to Miami and then to WA. But that is also the most expensive option since you'd have to purchase a new ticket less than 7 days before the trip ( these can be very expensive). I think the Panama and Mexico flights are cheaper, and if you can somehow use that LATAM credit from SCL or SAO that would be a good option as well. All depends on the dates you need to travel. Check Google Flights for direct flight options. Good luck!