That was a very good showing for the US women but I would temper the enthusiasm a bit with a reminder that this was the US championship for the women and that there was only one US runner in the top 8. When a US championship is held in conjunction with an open race, such as we have here, we usually see a strengthening of the US field.
That said, 8 in the top 15 is still a positive sign. It used to be that a strengthening of the field caused by a US championship being held in conjunction with an open race like Boston would just mean that we'd see 3-5 US runners in the top 15 and maybe 1-2 in the top 10. While only 1 in the top 8 is still not a great sign, this means there is a wealth of depth at the moment and this kind of depth is what you need to have a few people break through and turn themselves into regular top 5-10 finishers.