Hikers are better prepared than many for handling disasters because we have a kit that can sustain us in primitive conditions and allow foot travel over long distances. We understand clothing needs, navigation, fire making, water purification, first aid, simple shelters and more.
I remember having some discussions after the Katrina hurricane disaster and the scenario of just walking out of the afflicted area. I live in earthquake and volcano country and be prepared is important to me. Carrying basics in my car is an easy thing to do. Having a little food, water, extra clothing layers and rain gear, gloves, walking shoes, a fleece blanket and signal gear isn't much of a challenge if you are used to organizing regular trips into the back country. A poly tarp, some rope and an old sleeping bag will cover you for some fairly extreme conditions. Google "bug out bag" to see how some people prepare a portable survival kit.
Covering "urban survival," my messenger bag has a flashlight, hard candy and granola bar, small first aid kit, sunglasses, bandanna, Leatherman tool, and small compass, gloves, hat, and a tiny FM radio. I went to long lengths to find a messenger bag with water bottle pockets and I head out with a full 27oz Kleen Kanteen every morning. Stainless steel water bottles have the option of being used for water purification as boilers, along with using MicroPur tablets. A can opener is a very good thing to have. Most Swiss Army knives have one, or an army style "P-38" can opener is tiny and cheap. The classic Altoids tin style survival kit is perfect for an always-with-you backup.
I do carry a survival keyring all the time. It is a small Versalink with a micro firesteel, Victorinox Classic, Fenix AAA LED flashlight, aluminum whistle, a micro spy capsule with daily medications, and another spy capsule with tinder quick tabs. The whole works is 2.6oz and it is the same one I carry for hiking. I also carry a Benchmade Griptilian folding knife.
Traveling with a knife is difficult if you don't check a bag. One option is to just buy a Swiss Army knife or other small folder when you arrive. You can mail it home when you leave if it is something you want to keep. I would expect to keep it at the hotel when visiting sensitive areas like St. Peters, the White House, etc. I remember going through security at the White House in 1993 and they didn't blink at my 3.5" pocket knife. Try that now!
I just got a Steripen which would be big on my list of travel gear.