People are acting all impressed with the PM for saying this, but this was the work of one crazy man, not an organization dedicated to destroying you. No one would let one crazy person influence your county, so I'm not surprised at the PM's reaction.
When you face an enemy group dedicated to destroying you things are far different - it makes you worried there will be more.
No one thinks one crazy person who was caught will do anything else.
After 9/11 there were enormous structural issues with the world order that made it easier for terrorist groups to proliferate. That's why the Treasury Secretary was in all the initial planning meetings- there were two prongs to our response, one financial, one military.
The military one was an unmitigated clusterfuck.
The financial one was a rousing success. We forced the world to tighten financial controls, largely ended anonymous banking, seized huge quantities of terrorist funds, and made it really, really hard for the people trying to kill us to get money and to move money around.
There was a financial War on Terror, and we won it. Just because the military side went so badly doesn't meant there wasn't a real threat.
I guess some of the people doing anonymous banking or with offshore funds were indeed terrorists. But most of the "financial war on terror" is about terrorizing payment processors and banks, not actual terrorists.
This was before the identity of the attacker was known and everyone was still suggesting muslim extremists.
Remember, the Norwegian police are not carrying weapons (unless they get permission), the Oslo police did not have a helicopter they could use, politicians were only recently somewhat given security considerations.
So all in all, given that this system will not change much in response to this is actually quite remarkable.
It should also be noted that this is not being treated as the work of a lone madman. The focus is now directed at right-wing extremist groups internationally.