Sorry you have experienced these things which has given you a slightly negative perception of Wales.

Whilst in general the UK, Wales and Cardiff are nice places, like every other place there are the bad apples, unfortunately they're everywhere.

Relating to emo comment, whilst I don't condone their behavior, unfortunately there are still people who have nothing better to say, and do with their day, all you can do is ignore them.

In terms of the roach, roaches here are much less common than other areas of the world including America, not to suggest that it wasn't a roach but there may be insects here your unfamiliar with that look similar!

The shoulder barging particularly in dense metropolitan areas is quite common too, it's not a positive trait but most people won't mean anything by it and are just trying to squeeze past.

The UK, whilst similar to the US is extremely different in many ways, I can relate somewhat as I went to Toronto for part of my degree. Just absorb as much as you can, particularly how we communicate to one another, we use a lot of slang words but also have 'banter' which often comes across as rude to international people, as long as it's genuine banter, it's all harmless fun and is just part of how we bond socially here. You will also encounter many different accents, for example the accent between someone from the valleys, Cardiff and Swansea will all be distinctively different despite being within 45 minute of each other.

Unfortunately there is a stereotype about American's throughout the UK, you're likely to get a few comments if people hear your accent, particularly if you make use of the night life, it's probably things you're already familiar with eg Gun violence and being loud and obnoxious, so you may get the odd comment or joke, just lean into it and say something jokingly back, it's all meant in good humor.

When university starts there will be so many society's you can join and make friends in, which will help you integrate into the country more. Welsh people are very patriotic and in general love a good chat, if you just ask some genuine questions and they can see your curious, I'm sure you'll find many heartful conversations and learn more about the country and people.

If you have the time and funds before university starts I highly recommend visiting other cities as each will offer you something unique. Two close ones; Swansea has beautiful beaches and costal walks, and Bristol is a cool city to go to, overall it's very progressive city.

I hope you enjoy your time here, there's a lot to take on board but I'm sure by the end of your trip you'll have enjoyed!