Last week, the Syrian government shut down the Internet across its entire country. Last year, the Mubarak regime did the same thing in Egypt. Renesys, an authority on Internet infrastructure and security, has published an informal report on the risk other countries face of similar occurrences of total Internet disconnection.
Renesys says that the risk of a country's total disconnection from the Internet is dependent on the number of service providers that connect it to the outside world. The more service providers there are, the more difficult it becomes to completely disconnect a nation. Renesys writes, "you can think of this, to first approximation, as the number of phone calls (or legal writs, or infrastructure attacks) that would have to be performed in order to decouple the domestic Internet from the global Internet."
There are four levels of risk. The first is for countries that have only one or two service providers. Unsurprisingly, Syria is among the 61 countries that fall into this category. Egypt falls into the next tier, with fewer than ten service providers. Most Western countries (including the US) are well protected using this (admittedly narrow) metric. Notable countries that miss the top tier are Portugal, New Zealand, Mexico, and perhaps surprisingly, China. The list of where every country in the world ranks can be found at the source link below.