To make a positive change in ranking of the U.S. in a category, we must have

Knowledge that a better score is possible
Metrics. Data that can be measured across countries and years
Ideas for improvements that can lead to better scores
A desire to make improvement
The resources to make the improvement
Action must be taken

The National Assessment Day is an attempt to give us the knowledge that better scores are possible.

By some measures, the U.S. scores will improve from one year to the next because other countries do worse, not because the U.S. does better. A country hit by a natural disaster may incur lower longevity. Countries engaging in war or economic crisis or plagues will doubtless score lower. Hopefully, when the U.S. considers our options for improvement, we only consider the ways in which we can improve ourselves, not the ways in which we can use our resources to reduce the scores of other nations.

Barriers to improving US Ranks:

American exceptionalism. If we believe we are already the best, then we are unlikely to attempt to make improvements.
Patience/time. We need to make changes with long term lasting effects, not changes to increase our score next year, but with worse results in future years.
The rest of the world is just getting better - give them credit.
Disagreement about how to improve.