It’s a good question, Mehrdad, and it deserves a serious answer.
Language has functioned as a cohesive social force, much longer than the nation state has. Language has long bound people within an ethnic group, and those outside the ethnic group who also speak it. Language, it is true, is emblematic of ethnic groups, and is named after them. But that bond has never been so strong that the language has to be renamed, when the language spreads beyond the initial ethnic group.
And in fact, languages do not change name very often. The main motivation for changing a language name is when the old ethnic group no longer exists, and the language becomes primarily associated with a new ethnic group. You can argue that’s what happened with the Romance languages.
But English people still exist, and most Americans don’t object to their language being named after them. The English language is important to American nationalism, but the constitution and the flag are more important. The spelling and the dialect of English are unique to America, and that is enough for American nationalism. The name doesn’t have to be unique as well.
Based on historical precedent, it would take a cataclysm for English to change name. Most likely a cataclysm through which English people no longer understand Americans.