The bully's threat, intended to force Ukraine to investigate Hunter Biden, has made Ukraine realize that the US is not a reliable ally. Indeed, the US government is hardly a reliable actor at all.

I've often seen right-wing interventionists insist that the US keep supporting a tyrannical client government to show it is a "reliable ally." I think, on the contrary, that it is good to show rulers that they can lose support if they attack the people. But this case is totally different. The bully made the US unreliable, not because Ukraine had done anything wrong, but only because he demanded what he was not entitled to.