"Is due process the wrong term? Can't due process occur after the fact?"

Yes, it can occur after the fact. At least in the US, it's a complex balancing act whether you get pre or post-termination notice/hearing.

For example, deprivation/termination of social security benefits only require post-termination hearing.

http://en.wikipedia.org/wiki/Mathews_v._Eldridge

Welfare, on the other hand, requires pre-termination notice + hearing

http://en.wikipedia.org/wiki/Goldberg_v._Kelly