Err, the Soviet Union wasn't destroyed - it was dissolved.
If you go by the course of events, it's clear that "radical islamic terror" is dissolving fast. I guess the prospect of 77 to 99 virgins in heaven is not as appealing as it used to be 500 years ago, when you could look up and not know what's behind the ozone layer. ISS > ISIS
The 9/11 attacks were devastating, powerfull shock and awe (and provoked a complete and counterproductive response, most likely leading to a decade of terror recruiters bonanza)
Paris attacks were wicked, still powerfull, with assault weapons and trained fighters supported by a network.
Brussels Bombings, too.
Berlin was already a clear step down. The best they could send from a "talent pool" of a billion was one lone wolf with a gun and a truck? The best he could achieve is getting germany closer together?
The two attempted attacks in Paris were nothing. Lunatics attacking heaviely armed police/military?
London was in that realm, but unfortunately still too lethal.
Either islamic terror is running out of recruits pretty hard, because that medival ideology holds not much sway in a modern society or police/intelligence has done a much better job at containing it and destroying it's once certainly powerfull networks than we give them credit for.
Or both.
After the Paris attacks, I think many were scared of a constant stream of heaviely armed assailants. That proved to be wrong.
Calm down, stay alert, don't forget to actually still live your life. You'll die one day, irreregardless of circumstances.