My suggestion: linguistic colonization. And here's why:
Some will deny that anything out of the ordinary is occurring here, and thereby refute the very question OP has presented, while others will suggest that the phenomenon OP refers to is merely the normal linguistic diffusion that has always occurred, and therefore suggest the employment of an established term, such as “adstratum”, “linguistic borrowings”, “contamination or pollution,” etc.
"An appropriate term for the 'contamination' of a language." The title of the OP would suggest the need for a term equal in strength to "contamination" rather than a term equivalent to "normal" linguistic "borrowings."
And I would agree that the hyper-accelerated pace of today’s linguistic diffusion, and its resulting impact, is unprecedented and can best be understood by relating it to a concomitant phenomenon, that of "invasive species,” (certainly a form of ecosystem contamination) the term used to describe the egregious diffusion of biological species from previously indigenous habitats into novel or foreign territory. See, Wikipedia “Invasive species” Link
Just as the invasive species phenomenon is largely driven by the exponential increase in international trade and travel resulting from the integration of modern transportation systems with modern communications technologies, so too its linguistic counterpart, which I will refer to as, "linguistic colonization,” is largely driven by modern technologies of mass communication (i.e., cinema, TV, the PC, the internet, and a plethora of mobile devices).
An "alien species" plays the biological role in the invasive species phenomena that "linguistic colonization" plays in the linguistic contamination OP seeks to describe.
While I personally admire the term “adstratum” and, to a lesser degree, "pollution," these terms wholly fail to convey the virulence of a word such as "contamination" and are inadequate to describe the speed, force, and breadth of the global domination of English terminology that OP refers to, for example:
The following excerpt, loosely translated, is taken from the same LINK as is provided in the OP:
[T]he percentage of English loanwords has increased 773% in eight years. And how could we argue against these figures when English words are used daily by the mass media, words which could easily be substituted with their Italian equivalents. We've (Italians) become so used to using these English terms that we struggle to translate them in Italian.
The English Language in Nigeria:
Nigeria is a multilingual nation where English Language has acquired the status of a second language to many people, while it is a third language to others. It plays a significant role in education, politics, government administration, the judiciary, economy and legislation. English today can be regarded as the lamp with which the youths can travel through the education tunnel (Ige, 2000). It is even now being referred to as one of the major Nigerian languages (Ogundare 2004). See academy publishers
Today’s progressive technologies and the globalization of mass media are driving an phenomenon which some feel is rapidly dissolving the historical boundaries between segments of society, societies, and even nations. This is known as “cultural convergence" or "cultural homogenization.” Culture is the integrated and dynamic social system of behaviors, characteristics, customs, language, artifacts, and symbols that distinguish one social group from another.
Foundation for Endangered Languages
The FEL manifesto
1. The Present Situation
At this point in human history, most human languages are spoken by very few people, but that majority of languages is about to vanish. The most authoritative source on the languages of the world, the Ethnologue, lists nearly 7,000 living languages. Population figures for just over 6,000 show that:
• 52% of languages are spoken by fewer than 10,000 people
• 28% are spoken by fewer than 1,000
• 83% are spoken only in single countries, and so are particularly exposed to the policies of a single government
At the other end of the scale, 10 major languages, each spoken by over 109 million people, are the mother tongues of almost half of the world's population.
Some of the forces which threaten languages are clear: the impacts of urbanization, Westernization and global communications grow daily, all diminishing the self-sufficiency and self-confidence of small and traditional communities. Discriminatory policies and population movements also take their toll of languages. See, the Foundation for Endangered Languages Link
Related, of course, to this phenomena is the accompanying (and very real) fear of languages becoming the equivalent of endangered species.
There is a general consensus that the loss of languages harms the cultural diversity of the world. Many projects are under way aimed at preventing or slowing this loss by revitalizing endangered languages and promoting education and literacy in minority languages. Across the world many countries have enacted specific legislation aimed at protecting and stabilizing the language of indigenous speech communities. see Wikipedia “endangered language” Link