Hey so before I start I just want to say that everything in my review is my opinion and if you disagree with anything, feel free to ignore it. That being said, let's get into the review.
Videos: Starting off with the actual videos, I think the biggest problem with your videos is the lack of storytelling. In your first and third videos the problem is that there is no introduction or explanation at the start of the videos to explain what's going on meaning that as a viewer we are thrust into the middle of a story without really knowing what is going on meaning that as the viewer we have to try and pick up the pieces and fit them together ourselves to try and understand what is happening. In the second video, although you do explain what is happening at the beginning of each activity, the time spent on each activity is way less than the explanation which makes it feel almost like there is no middle or end to each story which means that the video almost becomes you telling the camera what you are going to do periodically throughout the day without you really showing you doing anything, which gives the video a jagged, staggered feeling and it means that the video doesn't flow nicely or feel coherent. At times it feels like you say something, forget to vlog for a bit realise and then scramble onto the next thing.
I think you should dedicate more time to telling a complete,, coherent story in each video. A story that has a proper introduction, climax and ending. If you're going to do something, explain beforehand what you are going to do, then vlog or take b-roll of you actually doing the thing and then afterwards, have a conclusion and give your thoughts on what you just did. I personally think it would be better for you to vlog one event properly than to vlog the whole day but not tell a proper story. So yeah, better storytelling would be my main focus point if I was you...
Banner: The banner design is simple and nice. Only things are I don't really like the texture on the background. I think it would look nicer if the whole banner was just a single block colour. Also you haven't aligned it correctly so the space between the top line and the top of the banner and the bottom line and the bottom of the banner aren't equal. So right now it feels like something is missing from the bottom. So fixing this would make the banner seem more balanced. One more thing that I noticed is that your channel name is JustinAbroad without a space and on your banner it says Justin Abroad with a space so they are not the same so I would change either one or the other to make them the same to have a constant branding
Thumbnails: I like your thumbnails, especially your first and third video's thumbnails. They are simple but convey an emotion to an onlooker. I personally don't like the text on the second thumbnail because I am a big believer that a picture is worth a thousand words so if you can have a thumbnail without any text at all that can convey the same emotions to the onlooker I personally think it will look cleaner and better. So yeah... I would personally try to use thumbnails without words but the most important thing is to keep the thumbnails looking consistent
Channel Icon: Your channel icon is ok but you can't really see much in it, because your face is so zoomed out in it. I would suggest using a profile shot of your face where you can more easily make out the details in your face, just so people know from a quick glance that it is your channel
Titles: The titles are ok, they don't really stand out, but in the age of clickbait, not many things stand out anymore. I think that as long as they convey what's happening in the video and aren't misleading I won't really have anything bad to say
SEO and promotion: Whatever you're doing, keep doing it. I don't know what you're doing (I want to though...(wink wink...)) but it seems to be working.... You're getting you're videos infront of a large number of people which gives you a greater chance of garnering a larger audience as your videos become better and better
I hope this helps. As I said in the beginning, feel free to ignore anything you disagree with; they are just my opinions and not law and at the end of the day it's your channel. And with that I wish you all the best with your channel