The English language used to be an asset of the US and UK. Now it has become a weakness.
Let’s zoom out from the Russian hacking of the American election. More broadly, hacking means extracting someone else’s information or inserting the hackers’ own information. English-speaking countries are particularly easy to hack because their enemies understand what they are saying. Being an English-speaking society is like living in a glass house: it makes you transparent. Conversely, foreign countries are opaque to mostly monolingual Britons and Americans. Foreigners know us much better than we know them. This asymmetry probably helped Russia get its favoured candidate into the White House, and it will handicap Britain in the Brexit negotiations.
The role of English has been changing fast. Until the 1990s Russia and China didn’t know much about what went on in western societies. Most Russian and Chinese anglophones had been killed or exiled after the communist revolutions, and were never replaced. Even the KGB was short of English-speakers: much of the intelligence sent to Moscow by British spies Kim Philby and Guy Burgess was never translated.