While .com doesn't define a single country, there was a huge development of US .com sites (and the internet in general) before there was much of an internet presence outside the English speaking world at all. In fact since most browsers (early and modern both) came out of the US, there wasn't even support for some non-roman character sets until later. That's how history went.
Furthermore, English is the single language widely use by travelers, heard in movies and even in local pop songs all over the world. English is the one language in which nearly anyone on the internet can recognize the name of their own language. Anyone in Russia could recognize that "Russian" refers to their own language, but how many Spaniards would realize that "スペイン語" was what they had to click on a Japanese site to find their own language?
Anything other than English would be a terrible default for a .com
Furthermore, English is the single language widely use by travelers, heard in movies and even in local pop songs all over the world. English is the one language in which nearly anyone on the internet can recognize the name of their own language. Anyone in Russia could recognize that "Russian" refers to their own language, but how many Spaniards would realize that "スペイン語" was what they had to click on a Japanese site to find their own language?
Anything other than English would be a terrible default for a .com