When a story begins with "the US says", is there any reason to believe anything that follows?

This is on my mind because I'm trying to make sense of this story.

The US says it has evidence that Russia has been firing artillery into Ukraine.

I don't know if they have, but the point here is, if the Yanks claim it to be true, does that claim make it more or less likely to be true?

Given the sheer volume of American lying that's shaped history over the past couple of decades, should we give them the benefit of the doubt?

I think it would be prudent to doubt the benefits of giving them the benefit of the doubt.