Yes it is very certain that american students are the worst in the world and will never beat Slovakia in any educational domain. They are proclaiming to be the best but the statistics don't say the same, they come in the bottom of the results in all fields, including the ones they think they are best.
Americans are falling behind many countries, including Slovakia, when it comes to education. We focus so much on standardized testing that we don't ever take a step back and see what actually works for our students. In Slovakia and many other countries, they have a multitude of classes that occur fewer times a week so students get a broader range of topics. They also have to pass entrance tests to place them correctly. Americans don't so those things, so we are greatly falling behind.
Using a degree as a basis for judging how good a student is is ridiculous. Students drop out for a number of valid reasons, such as disinterest in completing the program and cost, but neither of these indicate whether a person is a good student or not. There are many great students without a degree who had a variety of reasonable reasons not to complete their program.
A college degree is not necessary for success in the United States or anywhere else in the developed world. In fact, some students can be worse off after going to college because of their high debt level. It's important to continue education, but this can be done through non-traditional methods, such as trade schools or apprenticeship programs. Finishing college isn't the only measure of success.