Studying in United States is a way different than in Poland. In October 2008 I started Bachelor of Science at Wroclaw University of Technology (Poland). In Fall 2011 I was exchange student at the Kansas State University (USA). After that I camealt back and graduated at WUT (Wroclaw University of Technology) in January 2012. Then I started Master of Science (in English) and I also applied for Master program at the KSU (Kansas State University) and UA (University of Arizona) for Fall 2012. I was admitted to both Universities, but I didn’t get assistantship offer (to be Teaching Assistant or Research Assistant). Everybody knows that studying in USA is pretty expensive, but not when you have assistantship. Then department is paying for your tuition and you have salary/scholarship, which enables you to cover living expenses (such as rent apartment, food etc.). However I got an RA (Research Assistant) offer from KSU in July and finally started Master program in Spring 2013 (because it was too late to make VISA related issues done before Fall 2012).
In USA there are Fall and Spring semesters. Fall starts usually in the middle of August and ends in December before Christmas. Then there is winter break till middle January. After that Spring semester starts, and it ends in mid-May.
One of my friends (who got PhD at KSU) said that the difference between KSU and WUT is that KSU gives you real opportunity to learn something: it is easier to get good grades but it is also easier to learn a lot. I agree in 100%. The standard amount of classes for Undergraduate student (Bachelor degree) is 15 credit hours (30 ECTS), which is about 5 courses (usually one course has 3 credits). At WUT sometimes I had 10 courses. The standard amount for Graduate Student (Master or PhD) is only 9 credits (3 courses). It is not because it is easier, but courses are more time consuming. That is because there is much more to learn than in typical 6 ECTS course in WUT. Usually Master Student is also TA (Teaching Assistant) or RA (Research Assistant), which means additionally 20 or more hours. Last semester I took one class, which consumed about 10 hours (excluding classes) per week for me (you can find estimated work amount here). It is like 2 hours every day, and I had two more classes and research. As a reward I learnt a lot.
Another difference is that there is no strict list of courses you need to take. In Poland, all students from the same major has the same classes (only in last two semesters you can choose specialty but you still have the same classes with ~40 people). In USA, student choose courses on his own. There are minimum requirements, but usually you have a choice to pick one of a few proposed courses to satisfy one area requirement. You can find a degree requirements for Master degree in my department here.
Sometimes in WUT it is enough to study only one day before exam (if there is no laboratory or tutorials for that course). Here in USA it is impossible. You need to study every week, because of homeworks, quizes, required reading etc. In some courses there are quizzes in every week. Additionally ‘quiz’ not necessarily means ABCD. In my department it is always open-question test. The 90% of International students coming here for exchange from Europe, after two weeks says: “In last two weeks I was that busy like in finals week at my University”. In last semester, the day before semester start I received an email that I have a quiz in my first class and I need to be prepared for it (by reading given materials).
In USA everybody cares about studying. Students are not playing games during the lectures. Even when lecture is not obligatory, almost everybody is there and they interact with instructor a lot.
Disclaimer: All information given above are based on my personal experience. Everything can be different depends on the University, Department and even course you take.