What makes Argentina so formidable is not just that they're so good in forward areas and have technicians like Mac Allister and Fernandez in midfield - it's also that they have so many warriors in their team.
I have noticed it for a few years now - something switched and they started showing so much more fight on the park. By that I mean they are first to every tackle, they block off passing lanes, they read the game well and intercept so smartly. Even when they make a mistake, like a stray pass in midfield a few minutes ago. Against other teams Canada would have forged a chance, but an Argentina defender (think it was Romero) won a last ditch tackle. And they have lots of players who have that fight in them - Dibu,Lisandro Martinez, Romero, Molina, De Paul, Mac Allister, Alvarez etc. They're a team of fighters as well as technicians, and are not afraid to get stuck in like other South American teams. But they also have more quality as footballers. It's just so noticeable how they win so many challenges and read so many movements, and that (and the goakeeper) is what accounts for their clean sheet record.
It's that blend of brilliant technique as well as heart and fight that makes them so stong.