Firstly, that is your interpretation of zero. It is also an abscence of all the possible values that it could be, which is a plural concept.

Secondly, yeah American English is moronic and full of barstadised phrases. In the UK, we always say "by accident". We also say "I couldn't care less" not "I could care less", the American version which is illogical. If the meaning is to be "I care the minimum amount possible", then only "I couldn't care less" makes sense. The American version implies that you actually care a significant amount.