>>212812359Because North America hosts the best terrain in the world apart from Europe for industrialization and federalization.
Meanwhile South America is plagued by uninhabitable jungles, historically low population and a really tough terrain to maintain a federal government, to the point that a national program needs substantial concessions to regional governors up to this day.
Meanwhile in the USA after the Civil War federal power was mostly consolidated and strong, leading to imperialism and substantial industrialization, it also helps that the british were keen on investing in the USA and building railroads all across the USA. But even so, Brazil was somewhat of a regional power in the XIX century due to its european monarch and due to the european powers seeing an ally in south america.
But after WW2 with the European powers basically killing themselves, the USA became the sole hegemon of the Western Hemisphere due to having the biggest navy of the world and the reserve currency of the world. Hence all the decisions of the continent basically followed Washington's leadership, including the economic hegemony in the region.
But with the increase of population due to european immigration, the industrialization of the country during WW2 and the military dictatorship, despite USA, and the agrocultural export economy, Brazil is a much better position than what it was during the 60s