From 1870 till 1930, or even till 1945, the most influential partner in trrms of trade and investment in the Southern Cone was Great Britain. Germany was also influential in the inmediate years before WWI. The US was not that important, neither in terms of economical or political influence. All that began in around 1930, and consolidated after 1945.
It didn't last that long: nowadays, for many southamerican countries, such as Argentina, Urugusy or Brazil, China is one of the main trading partners, often surpassing the US. It is also an important source of investment flows. The US cultural influence remains unchallenged, but its political influence has greatly diminished since 2000.
Its no wonder the new Presidents of both Brazil and Argentina (both Center-right) are currently in China. Tweenty years ago, a Brazilian president would probably go to the US before travelling to Asia, as Temer has just done. An importat factor to consider is that both are center right, and have no traces of Antiamericanism as their more left-leaning immediate predecessors might have had. Yet they chose to go to China, cause its China who buys most of what we produce (as European or North American countries did in the past).
I am refering to South America, and mostly to its Southern Part. Mexico, Central America and the Caribbean are a different matter, as there there is a lot of trade with the US, and migrants from these countries to the US sent significant amount of money to their home countries that are important for their economies. That is way the US has a great influence there.