Well, my first ultrasound was at 4 weeks to confirm pregnancy, nothing to see except changes to uterus and body preparation for baby growth. So far, I know my uterus is long and a very accurate due date (Nov 23). No indications if I'm carrying a singlet or twins.
I went to a free clinic and got one before. At ten weeks
I live in Eastern Europe and here we can go to our first appointment since 6 or 7 weeks already, they always do ultrasound also to confirm pregnency. And then next us is about 12 or 13 weeks. I was also surprised that in US the first ultrasound is so late.
My doctor did a dating ultrasound at 9 weeks. I suppose different Dr's and countries have different ways of doing things.