I would say that the Boxer Rebellion was simply the last in a long line of events that weakened China relative to the powers that occupied (but did not actually colonize) that country.
The Boxer Rebellion did not really change the political structure in China in any great way. The Qing Dynasty did not fall, the Western countries did not actually take control of the country, but neither were they expelled.
The Rebellion simply underlined the weakness of the Chinese government and gave the West and Japan more power over China.
The Boxer Rebellion, and the aftermath of an international army being sent by the west to crush it, had the long range effect of denying China it's autonomy and independence for decades. More than a million Chinese Christians were killed by the Boxers, an anti-Western, anti-Christian uprising, and the major empires reacted with force to protect their interests.
China was then carved into "spheres of interest" where each country controlled trade in its region. America's Secretary of State, John Hay, issued the Open Door Note, demanding American trade access to each region of China. The Boxer Rebellion so weakened China as to render it nearly powerless for decades, including during World War II when the Japanese Army moved through China almost at will.
Due to this rebellion, the Qing dynasty grew weaker and weaker. The rebellion, along with the ensuing problems regarding some European nations caused the downfall of the dynasty. Then the People’s Republic of China emerged. It is China’s current government, thanks to the “Boxers”. Missionaries also stopped coming to China, and the West and many great powers stopped trying to colonize the country as well. The affects can still be seen today; the present government came about towards the end of the Boxer Rebellion.
The Boxer Uprising, an anti-foreigner movement, had developed in northwest Shandong between 1898-1900, as a response to the provocations of Western missionaries and their Chinese converts. Most of the Chinese population was not interested in the Christian message, especially in the evangelical and intolerant form that many of the Western missionaries were preaching. The Boxers were mainly peasants, who believed that their magic martial arts training made their bodies invulnerable to modern guns. With this belief, they viciously attacked Christian missionaries and converts, calling for the ending of the special privileges enjoyed by Chinese converts. The Dowager Empress Cixi, frustrated with the growing demands from the West, decided to support the Boxers against the foreign powers, which only invited a military suppression by an Eight-Nation Alliance in August 1900. The army, consisting of soldiers from Japan, Russia, Britain, the USA and France, managed to suppress the Boxers and drove Cixi and Emperor Guangxu to the West. A formal peace treaty, known as the Boxer Protocol,was signed in 1901, in which the Qing government agreed to pay indemnities for the damage caused to the lives and properties of the imperial powers. The Boxer Uprising laid bare the weaknesses of Qing China and severely weakened China’s position in regards with its relations to the West.