Twitter, in the end, is an American company. If it was Canadian, I'd think it should comply by Canadian law. The other option, of having it comply by each country's own laws (the German example is obviously a rather tame one) is needlessly restrictive.

That various cases you refer to seem wrong (I don't really have all the data) but I'm not clear why they make it OK for Twitter to potentially censor dissent in a dictatorship, for example.