Yes, Olympics will be held in Americas, but we still dont know where the Intercontinental Qualifier (where the weakest 4 teams play) will be organized. First of all, those teams should travel($$$) to this last tournment in order to get the last ticket to Rio. Talking about Americas, well, in 2004 the CSV OQT was played in Venezuela, but Colombia (which isjust next to the host) didnt send its team.
This situation has already happened. In the 2012 World Olympic Qualification Tournment, Peru replaced Kenya because the africans withdrew. In 2008, Peru or Kenya should have played a play off, but both teams dropped. Uruguay didnt aply and, finally, the spot went to Puerto Rico. And the last example I remember, Nigeria replaced Argentina in 2004.
That's why I said this could happen again this time. Of course, just if a european powerhouse or a FIVB´s beloved one doesnt qualify.
First, World qualifier and Intercontinental qualifier are the part of the tournament mane "World Olympics Qualification Tournament" host by Japan. It like Pool A is World qualifier and Pool B is Intercontinental qualifier.
Second, like you said No European teams replaced other confederations in World qualifier. So, I don't think so. About money problem I let you to read the FIVB sport regulation and the regulations of NORCECA competitions in order to find money is a problem, isn't it? Because, my english is not good, I do not know whether I can understand it true.