I'm the 00:42 PP.
You should be aware that the approach to studying and taking classes at European universities, including Trinity, is quite different, than at a typical US university.
I went to Trinity's history department site and looked up the courses on offer. Below is a typical one for freshmen. Read it carefully.
https://www.tcd.ie/history/undergraduate/modules/freshman/popes-kings-crusaders.php
While the subject is interesting, note the following:
Contact Hours: 2 lectures per week and 6 seminars over the course of the term - this means you're sitting in a large lecture hall taking notes, and during the term you will also have six seminars, which are smaller groups usually led by a graduate student where you discuss the subject. Compared to a typical Ivy league course this is much more listening to a droning professor and taking notes, and less open discussion (a term is approximately three months, so that's roughly a seminar every two weeks).
Assessment: 20% essay, 80% examination - oooh! This is very critical. While it doesn't tell you the frequency of examinations but based on my experiences with British universities, the vast majority of your grade is based on the final examination. This 80% could very well be exactly one exam at the end of the course. By comparison a typical US history course will have more frequent essays/papers, shorter assignments and quizzes/mid-term exams. The final exam, while important, isn't so heavily weighed. The ratio between papers and exams is more balanced.
What does this tell you? It tells you that European universities really do expect their students to take far greater responsibility for their studies and far less hands holding. There's pros and cons to this. The pro is that it forces greater discipline, the con is that so much of your grade rests on the final examination and blowing the final for various reasons is too common. And the con is also that it forces a "cramming" approach to studies, which is not always beneficial. In theory a typical student at Trinity or UK or European university spends most of the term reading their assignments (and you in theory do read a lot) and attending the lectures) but that structure too easily lends itself to blowing off your studies till the final weeks and cramming to catch up. Having experienced both an Ivy undergraduate and studies at British universities, I found the American education approach as at the Ivies more consistent and balanced throughout the semester with less of a counter productive crunch towards the end, it was just more well-rounded altogether. Last, but not least, grading standards tend to be different. Not better, but different. The idea is that an A equivalent grade is rarely given out so the equivalents of Bs are the equivalent of As at American universities.
http://www.globalinksabroad.org/upload/gud/program/program_guide549.pdf and it may have an impact on the GPA if the school doesn't weigh it when converting it to Columbia grades.
By the way, I am also intrigued by how it's possible to two BAs in only four years? If you start at Trinity and study, say, history, do you only study the history courses for two years, and then when you get to Columbia, you have to catch up with the rest of the distribution requirements that your peers have likely already finished with in their first two years? I wonder what the implications are for the last two years at Columbia? Just a thought. It seems to be a brand new program.