I have Prime and I pretty much get nearly everything on time or a day earlier than promised. Usually, I get surprised to find a "2-day shipping" item sitting on my steps the day after I ordered. Even when I didn't have Prime, I had little problem. I've had delays due to natural disasters, which are understandable, or supplier issues.
And I don't believe in stuff like "US is bigger"
... I'm pretty sure the US is bigger, actually.