World languages have been affected in two main ways by imperialism.
First, many languages have been altered as they have come in contact with the languages of their conquerors. For example, English was changed tremendously by the Norman Conquest in 1066. The language of the Micronesian island where I grew up has many Japanese loan words because Japan occupied those islands between WWI and WWII. Thus, languages both big and small have been affected.
Second, many languages have disappeared due to imperialism. This has come about because the speakers of the language have been killed off in large numbers. It also is caused by the speakers of the small languages being absorbed into the imperializers' society. An example of this is that the Hawaiian language has very few native speakers today (though efforts are being made to revive it).