That may be true, the finances aren't there to support the top players remaining in Brazil or Argentina, but they produce enough talent to be competitive in head to head matches and traditionally did better in intercontinental compeitions, though the Spanish teams have started to dominate that in recent years.
The Premier Football competition is not any European league however, its the World Cup. The most recent World Cup Final drew over 1 billion viewers across the 90 minutes (averaging 500M plus), compared to about 380M for the Champions League Final. Entire countries will shut down during their nations games, and many of the greatest cultural touchstones in Irish history over the past 30 years hinge on World Cup (or European Cup) games.
South American teams have always been extremely competitive at international level. Since 2000 there have been 5 World Cups, with the 15 semi finalists from Europe, 4 from South America and 1 from Asia. Though in that time the last South American winner was Brazil in 2002, and Argentina in 2002 were the only other finalist.
UEFA has 55 members, and usually gets about 13 places at each world cup, while CONMEBOL has just 10 members and gets 4 or 5 (the 5th decided by a playoff with another region).Though like with the Club World Cup, it is apparent that in recent years European teams are performing better than their South American counterparts