The reason why they call it Avenue of the Americas is because the street was officially renamed in the year of 1945 by then Mayor Fiorello LaGuardia to honor Western Hemisphere unity encouragePan-American tires.
The name Avenue of the Americas aimed to rebrand the formerly dingy street, by improving it's image after the elevated train line was removed and attract consulates and businesses from Central America and South America.
In the 1950s, 300 lamppost medallions featuring coats of arms from Western Hemisphere countries were also installed to solidify the name of Avenue of the Americas.
Although despite the official designation, most New Yorker's still refer to the street as sixth avenue.
And at the time of the renaming of the street, some people viewed it as being propaganda and also argued that changing all the city maps, street signs and subway markers was not necessary and the Avenue of the Americas also has various statues, which honor figures from the Americas like Simon Bolivar, Jose de San Martin and Jose Marti.
Both 6th Ave and Avenue of the Americas are the exact same street in Manhattan, New York City.
Although it was officially renamed "Avenue of the Americas" in the year 1945 to honor Western Hemisphere solidarity, most locals still refer to the street as 6th Avenue.
6th Avenue and Avenue of the Americas runs north-south and stretches from Church Street in Tribeca to Central Park South.
The street signs for 6th Ave and Avenue of the Americas says "Avenue of the Americas," although it is commonly called 6th Avenue, with many buildings also using both of these street names in their addresses.
The 6th Ave and Avenue of the Americas runs through Midtown and Greenwhich Village, and is situated between 5th Avenue and 7th Avenue.
The name change for 6th Ave was pushed by Mayor Fiorello La Guardia to celebrate New York's role, although the original name persisted in popular usage.
So yes both 6th Ave and Avenue of the Americas are the same street.
There's no difference in the street and it's just the names being different.
It can be confusing to some people, especially for those who are new to New York city and have never been there before.