Looks like they have been watching too much Die Hard 4. Hurray for ignorant politicians. Firstly, anything critical should not be connected to the internet, and odds are it probably isnt. If it is, it generally tends to be quite well firewalled, at least it was in any pharma site I was on. What they should be doing is making a bill stating anything important should be on a closed network, instead of some nonsense bill that sounds like a chinese solution to something getting on the internet the us goverment doesnt like.
Finally, the thought of a big off switch on the internet is pretty funny, the entire system was designed to allow of a comparatively small military computer network survive a nuclear attack. So in order to implement it they would have to install software/hardware in every single ISP, at a rather heafty expensive I would imagine.
Finally to top it all off, they want to protect there vital infrastructure, such as water, power and banking systems... by turning off another piece of vital infrastructure ? Are they idiots or what ? Do they know what damage turning off the internet could do to banking, businesses, science and society in general ? You may as well turn off the phone line incase some nasty terrorists are organising something over it. Maybe you should turn off the power incase they want to beat the president to death with a weed whacker.
The most laughable thing about this is, the biggest cyber-security threat is from denial of service attacks against critical business and government servers, so they cannot do business or inform the public. This was most recently seen in georgia when government websites were taken down by hackers during the war with russia. Hey, maybe it`ll teach those hackers when you beat them to the punch and do an ultimate DOS attack on yourself.