To the victors, go the spoils, and so essentially this is the most significant reason why English is the universal language in the world. Before the United States became the most powerful and the most influential nation on earth, there was the empire of the United Kingdom, which took its language to Australia, to India, to the Caribbean, to Hong Kong, to Egypt, to Canada, and yes, to America. America was not just founded by English speaking settlers, but also French, as well as Dutch, as well as Spanish, but it was the English language that became dominant in this country, because more English speaking colonists than any other colonist came to America, as well as the fact that Great Britain in conjunction with its colonists was consistently victorious over the French and its colonists in America.
Whether English is the "best" language, isn't really relevant, it is, with the exception of your native language in your country of origin, the most important language to have knowledge and proper use of as it is necessary and most conducive for diplomacy, for business, for the internet, and for education, to which it is beneficial for all parties involved. This does not mean, however, that you can't be successful without knowing English, of course you can, what it does mean is that it is far better to know and to be able to apply English for those that are motivated to be successful and worldly wise.
The Biblical story of the Tower of Babel, to which the inhabitants of earth, were of one accord in language, but had also demonstrated their willfulness and obstinacy against God, ended with the confusion of not being able to understand each other, because they dared to defy God, and the Lord "… confound their language, that they may not understand one another's speech." (Genesis 11:7). Consequently, today, there are over 6,000 spoken languages in our world, whereas for ease of communication and understanding it would be far better to have a common tongue that all could relate to. That language exists today, in the form of English.
Language is incredibly important tool in order to not only properly communicate from one party to another, but also for ease of understanding of what the other party is trying to communicate to us. While one can demonize another for myriad reasons, it is far easier to do so, when the other person not only doesn't look or behave like us, but doesn't communicate in a tongue that we can understand, making it easier to dismiss the other person as uncivilized, stupid, or nor worthy of our respect. This type of disrespect and misunderstanding can lead to fights, to disputes, and even to war.
In America, we have done a poor job in learning other languages, to which most native born denizens know and can only speak English; to which I suspect the basic thinking is that since English is the universal language, why bother. Languages, however, do rise and fall in popularity and usage, so rather than being that "ugly American", it would be better to obtain and put forth the effort to learn another language, so as to do our part to make this a smaller and more pleasant world.