I thought I understood roughly how US "government shutdowns" worked: If Congress (the legislative branch) is unable or unwilling to pass a law authorizing the executive branch to spend public funds on running the government, civil servants can't be paid and so they naturally stop working. This continues until Congress manages to pass such a law.
However, the current shutdown was, if I understand the news coverage correctly, triggered by the president declining to give his assent to a "short-term spending bill". If that is correct, then the legislative branch has authorized the executive to spend some monies, and all that remains is for the executive branch to utilize that authorization.
Wouldn't that situation be more accurately described as "the government has gone on strike" (i.e. on its own initiative, to put pressure on the other branches) rather than "the government has been shut down" (by an outside influence)?
Or, asked in a different way: If the president wants to halt government work, why would he need to wait for an opportunity to veto an appropriation bill? Can't he just at any time, embodying the executive branch, decide not to spend all the money he has been authorized to?