I have a somewhat different kind of suggestion for what would most improve math teaching in the United States. See some of my favorite articles on the subject by mathematicians

http://www.aft.org/pubs-reports/american_educator/fall99/ame...

http://www.ams.org/notices/200502/fea-kenschaft.pdf

http://www.aft.org/pubs-reports/american_educator/fall99/ind...

http://arxiv.org/PS_cache/math/pdf/0503/0503081v1.pdf

for the idea that proper mathematical education includes learning certain facts by heart through practice, but also includes a lot of flexibility of thinking and making deep connections between seemingly unrelated subjects.