As we've seen in Israel, the vaccine effect takes a few weeks more to kick in on a large scale to see it in the numbers. There shouldn't be much effect in the US yet.
People testing positive now might have gotten it a week ago, and we'd expect them to be two weeks after the second shot at that time to not catch it.
So in reality, today's lower numbers are more about coming down from a big wave, than the vaccines. 6 weeks ago, not that many people were vaccinated to affect the country's numbers.