Empires aren't empires, and there are certain rules that guide why some countries were empires and others weren't. These rules changed a lot over time (and I bet a whole lot of empires were retroactively named so by historians).

Colonial empires were just really big and globe-spanning nations, and some of them are arguably still around. We just don't like to call them that anymore. The British Empire, for instance, dissolved into a bunch of nations that got together and formed a club, the Commonwealth (which is why Australia and Canada still have the Queen as their head of state, IIRC). The sun famously still doesn't set on the British empire because of the Pitcairn Islands, microscopic British territory in the Pacific. The Falklands are also still part of Britain. It's the same with many countries. Look at a map of the Caribbean: there are still a number of French and Dutch islands there. France keeps in touch with its former colonial possessions through the Francophonie, an organization of French-speaking countries. Portugal was the latest country to cease being an empire in that sense, when they returned Macau to China in 1999.

Many empires fell through war and revolution in the 20th century, such as the Ottoman Empire (1922), the last of the Chinese dynasties (1912), Austria-Hungary (1918), Persia/Iran (1979?), Germany (1918), Russia (1917), and others. Some of these go back hundreds of years. The British royal family lost their Emperor status with the secession of India in 1947. But many just fell apart due to decolonization.

The result of all of this that Western society has made an imprint on the world like no other. Some scholars talk about this being the final victory of Western imperialism (especially considering the global economy that conspicuously emerged after decolonization, and that favors the West above all), but I don't know. It's too early to say, really.