Final answer:
Brazil and Argentina are characterized by more advanced collective bargaining arrangements, influenced by their involvement in MERCOSUR, which is consistent with a progressive or socialist influence on their labor laws.
Step-by-step explanation:
The countries in Central and South America generally characterized as having comparatively advanced collective bargaining arrangements are often those with a history of progressive or socialist leadership that have influenced their labor laws and trade agreements.
Analyzing the presented information, Brazil and Argentina are likely candidates due to their involvement in MERCOSUR, which emphasizes social justice and environmental protection alongside economic development. While several Central American countries are involved in trade agreements such as CAFTA, the question highlights collective bargaining which is more directly related to labor relations and agreements within countries rather than trade agreements between nations.