It's also big in the Netherlands.. In the 90s they had the biggest number of phone taps in the world, and this is not per capita, but the absolute number! With a population a mere fraction of the US's.

However the Netherlands is a fairly honest country when it comes to statistics, so I wouldn't be surprised that the US still came out on top, but they just didn't report most of their taps for 'national security' reasons.

But something has really changed in the past 20-30 years. Before this there was no way to literally monitor everyone. It was too labour/storage intensive. You really had to be a 'person of interest' for some kind of (usually legitimate) reason.

Whereas now in this digital age (and with everyone carrying a portable listening device in their pocket) this is totally feasible and thanks to Snowden we know it's actually being done too.