Africa: 5+1 spots out of 53 teams (11%)
Asia: 4.5 spots out of 43 teams (10%)
Europe: 13 spots out of 53 teams (25%)
Concacaf: 3.5 spots out of 35 teams (10%)
Oceania: 0.5 spots out of 10 teams (5%)
Conmebol: 4.5 spots out of 10 teams (45%)
Clearly Europe is the strongest of all Confederations and Conmebol is second.
If we could join all the Americas, then there would be 8 spots out of 45 teams for 18% more in line to what Europe has.
I think that would definitely make the tournament better as it would promote more competition between the CONCACAF/CONMEBOL teams and ensure you don't have teams like Jamaica/Trinidad and Tobago qualifying at the expense of a good team like Uruguay. I guess it would make things harder for Mexico, but it can't be that exciting beating teams like Belize 7-0 in the early rounds when you could be playing big games against better teams. I'm sure Mexico could beat teams like Argentina and Brazil at the Azteca in any case.