Answer:
The development that most directly weakened European colonial states and contributed to the changes between the two maps was the Japanese occupation of Southeast Asia during the Second World War. The Japanese invasion and occupation severely weakened the colonial powers in Southeast Asia, and ultimately led to the emergence of several independent states in the region. The decline of European economies during the Great Depression, competition between Great Britain and France, and the conquest of Spanish imperial territories by the United States were also important factors in the decline of European colonialism, but the Japanese occupation had the most direct impact on the changes in the map.