I don't know about Euro or American overlords, and I don't think it's even the most pressing problem if Argentina is dollarized. I've lived for several years each in 2 countries that dollarized, Ecuador and Venezuela, and neither makes an attractive long-term case.
Ecuador is the more orderly of the two cases, as you'd expect, with dollarization coordinated with the US. Dollarization has turned it into a high-cost base country, with little FDI, Prices inflate due to the difficulty in finding small change, they get rounded (up, of course) to the nearest 1 or 5 USD. The banknotes deteriorate rapidly (I'm sure, due in part to the low quality), so the Ecuadorean central bank has the added expenditure of taking the damaged ones out of circulation and sending them all to the US to be replaced.
Venezuela's case is a mess, with no coordination with the US, so there's no mechanism to replace damaged notes, it's your loss if you've got one. The country has inflation in both USD and Bolivar, and is quite possibly already the most expensive Latin American country to live in (people survive with foreign remittances, "caja CLAP", and various subsidies. Low denomination banknotes are almost unavailable, again all prices are rounded up, contributing to inflation.
To link the huge pool of Argentinian dollars kept under mattresses here, plus dollarize the money in circulation, would be an enormous undertaking, and it can't really be done without official coordination with the US, which might very well not be forthcoming. Would the US like to add some $300bn, plus $50bn Peso circulation to the active USD circulation (I'm not sure how much of that is actually physically hiding under the mattresses here)? Where would we get small change from (nobody uses anything other than $100 notes here)? Plus, the tsunami of counterfeits courtesy of our friends in Peru would be a sight to behold. Before Venezuela stopped printing paper money, the almost worthless banknotes were scooped up, transported to Peru, washed, and reprinted as Dollars (a literal case of the currency being worth less than the paper it was printed on). If the Argentinian banknotes are retired, where would they go?
Milei & Co. just want soundbites, nobody is thinking this through.