Hola! Along with your funds you'll need FinCEN 105 to exit the US
https://fincen105.cbp.dhs.gov/#/ and OM 2249-A to enter EZE and Argentina
https://serviciosweb.afip.gob.ar/genericos/formularios/pdf/interactivos/OM2249.pdf (they make this hard to find online, I remember this when we had to find it months ago). The US form you can fill out online and then when you get to JFK you have to find where Customs is. DO NOT fill out the form online and then go through TSA and security without going to Customs. They wrote online that they could come to the gate and find you before the flight, and who knows what would happen then! The terminal we left out of at JFK, Customs was a nondescript door outside security down in baggage claim. You'll need to tell the officer(s) you filled out FinCEN 105 online and you have money to declare that's more than $10,000 (we printed out the form just in case). They will take you to a room and inspect/count the money, ask about reason you are transporting and the provenance of the funds, and then if all ok, send you on your way, where you can go up to security and to the gate. The process didn't take too long, but you'll definitely want to add at least 30 minutes--after finding Customs, there were a some minutes wait before someone came). On the Argentine end, at EZE, after passing through border patrol and getting luggage, you'll go to the "something to declare" line. There's usually no one going in that line, but usually there is a person sitting by a door. You explain that you have money to declare and that you've filled out OM 2249-A. Then the process is similar to JFK--they will take you to a room where they will inspect and count the funds. While we had papers and receipts to show the provenance of the funds and documents about our house purchase and why we were bringing the money into/out of the country, it was only in Argentina that they wanted to see those (but in the US, they do want to know that too so it would be important to have it ready to show in both places). And then you can be on your way.
As far as our bank in the US is concerned, I had personally gone to our branch location to ask about withdrawing a large amount of funds. I explained the reasons and the manager said it wouldn't be an issue and could be pretty quick. But when the time came a couple days later, there was a little more scrutiny from the higher ups at the bank, so we had to explain and submit documents about why we wanted to withdraw the large amount, where the funds came from, and (importantly for the security of them and us) how we were going to transport the funds from the bank. But once all of those concerns were answered satisfactorily, it was straightforward and quick to get the cash. Overall, our experience with bringing a large sum into and out of both countries was easier than we expected. As I mentioned months ago, even with hiring security on both ends (which in both places were very professional and surprisingly affordable--and ultimately cheaper than transferring the money and picking up cash through a casa de cambia, even with the very low rate we were offered) and which really did help to alleviate much worry and concern, overall it still was a nerve-wracking experience and the mind wandered into all of the possibilities of what could go wrong (crooked agents (in both countries), funds seized, someone stealing on flight, carjacking in BA, etc.). But in the end, with all of the preparation, it went off quite well (except for the horrible traffic from EZE to the escribano office and the closing) and we purchased the property with no problem!