For example, it was publicized of a person who detonated a 2 part liquid chemical explosive on an airliner (US) that only chemically flashed and did not explode - burning the terrorist and starting a small fire. The passengers jumped the terrorist and the fire put out. It was not inadvertent one of the chemicals was of a lower concentration level than he thought he had bought. A plot to use chemical bombs to blow up a subway station was adverted and the 4 involved arrested and prosecuted - all originating with a suspicious email inquiring of one of the two necessary chemicals - and then following emails, reaching into computers and tracking cell phones documented the plot and learning those involved.
Compared to much of the world, the USA has extremely low incidents of terrorism by explosives. However, it is actually the Dept. of Homeland Security and somewhat FBI that more undertakes such surveillance and investigations, though may use CIA resources.
I do not buy the mantra spouted as fact that the CIA caused the problems in the Ukraine. I believe it was Russia that stirred it up. If we wanted the Ukraine we'd have troops there now. We don't. Russia does.
It is clear that regime change was Obama's thing as was the Arab Spring. Agencies of the government follow directives of the president and basically are his employees and staff.