U.S. students often fail in math because the subject is taught ineffectively. American schools teach math as a series of rote memorization rules to be followed; however, mathematical skill demands creativity and flexibility in thinking.
Math is commonly taught as a series of facts with systematic answers. Math skill is gained by repetitive interaction with a series of problems with a familiar formula and systematic approach. Especially at higher levels, math needs to be approached as a challenging process that may not have an apparent answer.
Student's attitudes are also a factor. Studies indicate that older students may not be motivated to take math courses seriously.
Another factor is the standards of individual states. Many of the states have "proficiency standards" for math courses that are very low. Although students may be taking three or four years of math, the courses are "dumbed down," leaving students unprepared for college study or real world application of their skills.
The emphasis on grades puts a lot of stress on students. If they do not receive top scores, they may retreat from the challenge instead of struggling through it. Grading and evaluating the value in a mental struggle is difficult, while judging responses to common problems is easy. Math is supposed to be hard to continue to force the mind to struggle with solutions.