In my opinion, having an international language is a very important thing nowadays. Whenever you go the people of different nationalities speak English to understand each other better, you walk down the street - billboards and street signs are in English (mostly in Europe).
Global language is key to a conversation between governments, scientists, journalists, anyone who wants to communication! Isn't it amazing to have a chance to make friends and even business partners around the planet?
It also will help out tourists a lot! if you're in the crowded place and you accidentally push a person, you can apologize with a simple "I'm sorry" and people won't think that you act impolitely.
You can ask citizens about the places to visit and eat. And if something happens in the hotel room you will be able to report administration without having a problem.
I can say without a doubt that the global language gives people lots of benefits!
In conclusion, I'd like to say that everyone has to know at least a second language just to feel more comfortable in today's world.