Really, truly not an issue. Your opps will be the same whether you have one or two history degrees- and unless you go into academics / education, will be pretty much the same as with any other humanities degree.
“I’ve heard” is the most useless non-data source on which to base decision making!
Stop and think for a minute. Do you really think that everybody at Columbia is depressed? of course not. Are some students depressed? of course. What matters is whether you will find it depressing. Do you think that there are no ‘wealthy and snobby’ people at Columbia or TCD - or any ‘prestigious’ college?!
As for TCD ‘throwing you in the deep end’ (full disclosure- I used to teach there): in Ireland (and the UK) you are expected to be responsible for your own learning. The biggest challenge for US students (as your sister in Manchester will tell you) is that there is much less continuing assessment: your entire grade can be based on your final exam (though in practice in history you will typically have at least one other graded element), so you have to keep on top of your work yourself- if you are a procrastinator it can get ugly, In Dublin when the trees start flowering students know that it’s time to start getting serious about studying for exams, which are much more regurgitative (esp in 1st year) than you might be used to. Irish students will talk as if they aren’t doing any studying at all- but they are. If you go, do not believe anybody who tells you “I haven’t done a tap”!
Your time at both Trinity & Columbia will be highly structured, as you will have a lot of required courses.
But here’s the thing: they are such different things! me, I would love the Columbia Core, the Dublin experience and learning history from different points of view. My husband would not love the Core, but would love the freedom of Brown’s open curriculum, where he could study a huge range of things and maybe do a study abroad at (say) Oxford. I would love the immersion in two great cities, he would definitely not. And so on.
There is no meaningful difference in the objective metrics- both options will give you more opportunities than you can take advantage of in four years! But there is a very big difference in what they will be like experientially- and for that it really comes down to how they feel to you - not your parents, not people on CC. Just you. It’s exciting and scary and you just have to trust yourself and jump in, knowing that you will discover good and bad parts along the way, but that you will make it be the right choice. Welcome to adulting!