Each of these web sites has unique characteristics. Europeana is the richest and most extensive, including most of the national libraries of Europe plus numerous cultural agencies. Though content, which includes images, text, video and audio, focuses on Europe, it is nonetheless global. A simple search for China produced over 2,000 results!
Both the Homeland Security Library and the World History and Cultures Library are U.S. institutions. The former is particularly useful for current global topics. The latter has resources on both historic and current events.