Thank you for being honest as I think many expats are many times living in denial. I'm NOT saying locals aren't friendly because they certainly are. But as a 50% Mexican American citizen, I see plenty of ignorant ugly American tourists. The sad part is they don't see they are ugly.
I've spent a significant amount of time in South America, and I've observed that the 'Ugly American' stereotype, along with its counterpart, the 'Economic Refugee American,' is generally met with disdain. This is precisely why I consciously steer clear of individuals embodying these stereotypes. All my friends in South America, including those in Argentina, are Latinos, and they candidly share their less-than-flattering opinions about my fellow countrymen.
It's a case of reaping what you sow. Act like a stereotypical gringo, and you'll likely be treated accordingly. Conversely, if you approach interactions with humility and respect, your experience will be far more positive. I've never faced any prejudice due to my U.S. nationality here. So, there's no need to worry about it, especially in the metropolitan areas of Argentina. While concerns might arise in rural Colombia, the cosmopolitan regions of Argentina generally do not hold nationality against you.