I have a single question.
What happens if student from EU university , let’s say student of Erasmus University Rotterdam completes year 1 of bachelors successfully and then applies for transfer to US college, will he start in year 2 or year 3 of US college ?
This is something that cannot be predicted as each institution sets its own policies about accepting transfer credits.
It is entirely possible (albeit unlikely) that the student could be classified as a first year student, rather than as a second or third year student.
However,as a transfer, that student is no longer eligible for merit scholarships if American and no longer eligible for financial aid if international.
Financial aid for transfers is institution specific. Generally speaking, merit-based aid is better for first year applicants than for transfer applicants, and both merit-based and need-based based aid normally are better for US students than for internationals. That means that while it is not completely impossible for international transfers to find good aid, it is indeed extremely didficult for them to do so.
It is a really difficult question, and the universities will not answer it until you have been offered a place, when they will evaluate your transcript & tell you what credits they will accept.
Most of the Europeans I know are very confident that their first year of university is equivalent to the second year in the US, and therefore expect that 2nd = 3rd, but it is more complicated than that. The years of university are not as structured in the US as they are in most European unis- it’s not that you master a set level 1 and then move on to a set level 2.
Also, no matter what level you are notionally allocated to, the graduation requirements stay the same, so if there are requirements that are usually satisfied during the first year (often a writing course), you are likely to still have to take it. Once you have been accepted, the college will tell you what credits they will accept, how many more you need to graduate, and (either then or when you enroll) specific requirements you need to meet.