What is happening in Greece? Is this going to spread to other EU countries?

I'm a college student in the US. I don't even use dollars anymore as all my money is digital. I'm just getting really confused about how this could happen, with everything being digital is there not a way for the government to work with the banks to just bypass the lack of physical currency and just digital funds? Are there any similar scenarios in history where a country has gotten this close to economic collapse?