I think the 2 to 3 years estimate seems to be quoted more in articles by publications critical of Milei. I am not sure that estimate applies to two presidents who like to govern by execute orders. I suspect the immigration reforms announced earlier in the year by Milei might be related to the effort to get the approval for the US Visa Waiver Program. Meaning, the work started before the announcement this week.
It has been estimated that Argentina getting back into the US Visa Waiver Program could increase trade between the countries by $11 billion. If both presidents see it as a high priority, which I believe to be the case, I think the timeline could be greatly accelerated. Having it in place, at least for a subset of the Argentina passport holders in time for FIFA World Cup 2026 could something they are trying to achieve as others have noted.