Messi guided Argentina to their first trophy in 28 years – La Albiceleste dethroning defending champions and hosts Brazil in July's Copa final.
For Messi, it ended years of heartache and near misses after the superstar Argentina captain finished runner-up in the Copa America three times (2007, 2015 and 2016) as well as a beaten finalist at the 2014 World Cup.
As Argentina prepare for Thursday's CONMEBOL World Cup qualifier against Bolivia, six-time Ballon d'Or winner Messi discussed his first senior international crown.
"After so much suffering, lifting something with the national team was special," Paris Saint-Germain's Messi – Argentina's all-time leading goalscorer and most-capped player – told ESPN. "There was a part of the journalists that treated me as a failure and that I didn't feel the shirt.
"Everything I won was important, I was lucky to have won a lot of things in a row at my club and very fast and the blows came later.
"With the national team, it was blow after blow, that made it more important now. It cost a lot to get it.
"When we won, I couldn't believe it. I dreamed it so much that I didn't understand what was happening. Honestly, I enjoy it more now when I see the images than that moment."
Messi won a club-record 35 trophies at Camp Nou – including 10 LaLiga titles and four Champions Leagues – before sensationally leaving Barcelona for PSG on a free transfer in 2021-22.
"I don't know where I'd place it [Copa America triumph]. Everything I won was important but this was the most difficult," Messi said.
"A lot of things happened and I won very quickly at Barcelona. At the national team, it was one hit after another."
Argentina are in the midst of a 21-match unbeaten streak – dating back to 2019 – after Sunday's blockbuster clash against Brazil was abandoned following an apparent breach of coronavirus regulations.
Lionel Scaloni's Argentina are undefeated on the road to Qatar 2022 and Messi added: "You have to start by recognising that we are not the best in the world.
"We were not the worst before and we are not the best now."