Maybe saying there should be six nations games in America is taking it too far, because of the tradition etc as you say. But World Rugby is correct to want to promote the game in America.
Not only to grow the game but also to compete with NFL, since NFL is already targeting rugby countries for their growth, using this same idea.
Just yesterday the San Francisco 49ers played the Los Angeles Rams in Melbourne, Australia, in front of a sold out stadium.
Rugby will either compete and grow or go into terminal decline.