I would have some extra food, water, medicine, and cash on hand . . . just in case it happens here.
Why? It's sounds like you have no idea what is going on Greece.
Because people's thinking is if there is a total economic collapse they will have food, water, cash, meds. Maybe you are the one that doesn't know what is going on. Most of the banks have shut down. Guess what? Even if it is FDIC insured (which I doubt they have in Greece anyway) it will take time to get your money back. And the ATMs are restricted to $60 a day per person. Back during the depression a lot of things were rationed. And some things you could not even get. The line of thinking is if you have it stocked up then you will have it. But if it goes to that and people find out you have it then they will kill you and take it.
Could you still get food, water, medicine, etc. at the stores in 2008 when U.S. Economy collapsed? Of course you could. The panic about the Greece debt crisis, which has been going on since 2010, and needing to stock up on supplies is complete overkill. Sure, it has and will affect our financial markets, but this isn't some doomsday preppers scenerio.
The fear is that Greece will default on their debt. Is it realistic that the US will default on their debt? No, it's not. The US takes in revenue 10 times greater than it's debt payments. So yes, if you what is happening in Greece could happen in the US, you probably don't understand what is going on in Greece.