First, what do you want from yourself? In America, no one can know your grades except you, your teacher and your tutor without your permission. Including your parents. If they want to ask the school about your grades, they must get your permission. So, you don't want to study hard, people who want to control you don't know your situation, and people who know your situation don't care about you at all. You have full freedom. If you want to get an A in every class, you will be very tired. Usually get up at 8 o'clock every day and study until 12 o'clock in the evening. In addition, weekends are also used for study, not for parties and shopping. This should not be much easier than high school. If you get a B in every subject, you will live forever, so it is enough for you to attend classes on time and finish your homework after class.
Second, the fatigue of the United States is more reflected in the rhythm. The study of domestic high schools is to arrive at school on time in the morning and sit in the seat during class. As for how to do it, that's your business. Teachers don't know if they don't listen, play mobile phones or even sleep. Therefore, although the high school study time in China is long, the pace is very low. However, most courses in the United States are small classes of more than a dozen people, and there are many seminars discussed by everyone. The teacher also speaks very quickly, usually passing by, or sending some exercises directly. If you don't preview or get distracted in class, it will be difficult to keep up. So it forces you to concentrate in class without blinking. Just listen and remember. Although I only have three hours of classes every day on average, I think students are more tired than a day's class in high school.
Third, the holidays in the United States are very long, about four and a half months, while the holidays in China are very short, only about two months, and two months will be used for cram schools. But the four-and-a-half-month American holiday is not designed for you to play, but for you to find some internships or scientific research according to your own interests. As I said above, internship and scientific research should be regarded as high-tempo jobs, while cram schools are low-tempo. So if you find a scientific research internship, there is only one month left in the holiday, and the rest of the time is a high-tempo job, of course, you are tired. Otherwise, it's easy for you to stay at home or go out to play and go to college in America.
So whether America is tired or not depends entirely on you. Of course, you are very tired when you are demanding of yourself, even more tired than high school; You are more relaxed about yourself, and of course it will be easier to study in the United States.