You've asked for feedback specifically from individuals entering at Ezeiza whether they've been routinely, or randomly, questioned about criminal history since the new law into effect on 30 January 2017.
As @JonathanReez has pointed out that, since no such questions were asked during a recent land crossing, it is unlikely that it would occur during processing through Customs and Immigration at the airport.
Specific to your concern, and contrary to the opinion offered about US laws, only if US Federal or State officials have triggered an INTERPOL alert would entry into Argentina be a problem. And, should that be the case, it is very likely you would be prevented from boarding a direct flight, rather than be confronted by the issue on arrival.
The article you link to, and the announcement made recently, refers to Argentina adoption of the Advanced Passenger Information (API) system, an electronic data interchange currently in use many countries, including the United States.
The required information consists of full name, gender, date of birth, nationality, country of residence, travel document type (normally passport) and number (expiry date and country of issue for passport).
What else: airlines and the travel industry have a passenger name record (PNR), a database in the reservation system that includes passenger name, airline/travel agent contact details, ticket details (number or ticket time limit), itinerary, and name of the person booking, and information on payment, luggage, seating.
What will Argentina do with this information? Use it to check INTERPOL Criminal Information System databases.
Enacted on January 30, 2017, Reuters reported that
Argentina changed its immigration law to make it easier to deport foreigners who commit crimes and to prohibit individuals with criminal records from entering the country. The law, implemented by decree and not requiring congressional approval, also restricts those who are serving sentences or have criminal records in other countries from entering Argentina.
So, you travel to Argentina: can a Customs & Immigration official ask whether you've ever been convicted of a crime? Yes. Will they? Perhaps. Is it likely? This is difficult to establish less than two months on since the Presidential decree. Other countries do ask, randomly during an Immigration chat, and do use that information to equate the offense to their laws to determine whether a person is admissable.
However, your concern is valid and, although citizens of some countries do not need a visa to travel to Argentina, one way to overcome this hurdle is to apply for a visa.
The application does have many questions about entry and criminal histories, nine of them to be precise. The details asked range from sentences for trafficking (arms, human, drug), money (laundering or investment in illegal activities) or other crimes punishable by three or more years of imprisonment. The list goes on and on: genocide, war crimes, acts of terrorism or crimes against humanity, terrorist activities, prostitution, immigration offenses. They end with a broad question, whether the person has done anything that might be covered under the Argentine Act 25871.
One process employed by those whose past inhibit or prevent them from entry into a country is to request a waiver of that requirement, variously referred to as a Waiver of Inadmissibility. It allows them to demonstrate that those issues are behind them, they no longer participate in those activities, that they are rehabilitated.