The world's most influential languages

There is a natural monopoly in a lingua franca, or common tongue. The original lingua franca was a Mediterranean trading language that drew principally on Italian [1]; with modern communications and media linking the world, this monopoly is now global, and the monopolist is English. This became particularly clear to me last year as I traveled the world on a circumnavigation. In Thailand, the signs are in Thai and English. In Singapore, they are in Chinese and English. In the United Arab Emirates, they are in Arabic and English. In Ireland, they are in Irish and English.

English owes its status principally to the political dominance of English-speaking nations—roughly speaking, Britain ruled the world in the 19th century, and America ruled it in the 20th—but it's not a bad choice as languages go. It has a rich technical vocabulary, relatively simple grammar and syntax, and an alphabetic writing system based on the widely supported Roman alphabet. Its only plausible competition is Chinese, due mainly to the massive number of native Chinese speakers, but Chinese writing is so difficult [2] that it's hard to imagine it ever competing successfully with English: although the latter's idiosyncratic spelling is legendary [3], even a mediocre alphabetic system is still much easier than Chinese.

Some people worry that advocating the use of English is an act of cultural imperialism [4], but this issue arises only because for English speakers the native tongue and the lingua franca happen to coincide [5]. It's easy to see the fallacy if you consider the possibility of a different lingua franca; for example, if Swahili were the lingua franca, I would advocate its use, and would strive to master it myself. As luck would have it, I get to be lazy and coast on my native tongue, but if you haven't yet mastered English, it would be much to your benefit to do so.

[1] https://en.wikipedia.org/wiki/Mediterranean_Lingua_Franca

[2] http://www.pinyin.info/readings/texts/moser.html

[3] https://en.wikipedia.org/wiki/Ghoti

[4] http://www.catb.org/~esr/faqs/hacker-howto.html

[5] In physics, we would call this a degeneracy.

These ranking ignore the fact Spanish and Portuguese are much closer to each other than any other two languages in this top ten listing.

Although Spanish and Portuguese are now two separate unintelligible languages, they were virtually the same 800 years ago. Someone literate in one can easily learn the other; it's probably the same with fluency. Machine translation between them is probably very accurate because of their relative closeness and the huge volume of sample data for both languages. Also... Because of geopolitics, Brazil and the rest of Latin America can easily negotiate compromise agreements where they say "put the administrative center for this in Brazil and make Spanish the official language for it".

So perhaps there's more of a case to consider Spanish and Portuguese to be one language for these rankings, than there is to lump all the unintelligible Arabic dialects (Morrocan, Egyptian, Levantine, Iraqi, and Gulf) into one language, or the unintelligible Chinese dialects (Mandarin, Cantonese, Wu, Minbei, Minnan, Xiang, Gan) into one language.

English not being the official language of the US means some certain other countries could more easily accept it as an expedient language for international discourse.

There needs to be an international version of English designed so that it is simple to learn. For instance: one sound = one letter and all verbs conjugate the same.

You seem to be talking about a "potential" audience. Statistics for actual usage is quite different.