Why were only the european nations colonizers?

Others tried... and failed.

Japan tried to colonize China and China before that tried to invade and colonize Japan. African countries for centuries have invaded each other and tried to take over th other people's land and only the Zulu and Egyptians actually succeeded.... for a while.

Arabs colonized a good portion of Europe and had to be turned back from just south of Paris France in 732 and later than that in Austria. They did colonize northern Africa though and kept Spain until 1492! They had many parts of India until the Brits drove them out.

The Mongolians took land way out into Europe!

Where did you learn your history?

European countries were the only ones that had a need to. The core nations of the world at the time, the Chinese and Ottoman Empires, were rich, and had no need to invest in such risky venture. Europe lacked an empire, and consequently lacked the natural resources China and the Ottomans had. Europe had much to gain and little to lose with such a risky venture to sail to the indies. Even when the Europeans succeeded in their ventures overseas, silver would keep flowing from the colonies to Europe, and to China, as Chinese goods were in high demand in Europe. Britain later reversed the cycle through Opium. It was through its colonies that Europe became full of empires, as before it stumbled into the Americas, China and the Ottomans were the strongest empires of the world. The technology developed by Europe was not an end, rather, it was a means to acquiring the natural resources it needed, through the means of force, meaning that superior weapons were required to subdue groups who possessed the resources Europe needed. Do not believe all the crap people say that Europe is superior intellectually as a reason why they were able to become an empire.

They were the advance civilizations of the time with a centralized government and the motive for wealth and expansion. To be sure non European countries had imperial motives and did conquer territory such as America(Mexico, Hawaii, Cuba. Philippines, Puerto Rico) Japan, Russia...however these territories were already colonized although the distinction is minimal at best.

It wasn't, and they weren't.

But for the role they did have, see Guns, Germs and Steel.