European colonization in the Americas certainly had a negative effect on Europe if you consider the later years, when the European powers lost control of many of their American colonies, to be part of the colonial period. In short, the loss of territory in the Americas led to a period of rapid colonial expansion in Africa and Asia by the European powers called New Imperialism. Partially as a result of New Imperialism, we begin to see a rather complex web of alliances and rivalries spread across Europe and into Asia. This led to several decades of mistrust and strained relations between the European powers, culminating in the outbreak of WWI.

So I guess you could argue that losing control of many of their American colonies, which in my mind is still part of the colonial period, kick started a chain of events that contributed to the outbreak of WWI.