I have Global Entry so I don't interact with US customs officers aside from waving a receipt at them on my way out of the immigration hall. So I don't have expe

I have Global Entry so I don't interact with US customs officers aside from waving a receipt at them on my way out of the immigration hall. So I don't have experience of them. But my personal worst stories of border crossings all involve either Canada or Germany, for what it's worth. Canada's CBSA in particular seem to revel in it, yelling at you for asking a question, yelling at you for doing what they told you to do, and just plain yelling at you.