Can countries be blocked from the internet?

Without debating the actual impact, there is no doubt that the Russians actively attempted to interfere with the U.S. election by maintaining a massive "troll factory" and other stunts. Question: Do international internet connections pass through a central hub or something that could be closed? What would be involved in simply making it impossible for any site in Russia to access any site in the U.S., or vice versa? The newest sanctions seem trivial in comparision with the attacks.

Quote:

Sanctions also were imposed on individuals known as “trolls” and the Russian organizations — including the Internet Research Agency — that supported their efforts to undermine the election. Additionally, the administration alerted the public that Russia is targeting the U.S. energy grid with computer malware that could sabotage its systems.

https://www.washingtonpost.com/world...=.778dafe86e65

via International Skeptics Forum http://ift.tt/2phlLxN