Advice on going to Thailand or Western Europe

Hi everyone, I'm planning on an impromptu solo budget trip in late July and early August before I go to university and this is my first time traveling alone and staying at hostels. For some background I am a male, 18 years old from the US and have traveled a couple times before and also lived abroad in central america. As this is new to me--I have lots of worries such as not meeting anybody and being alone the whole time--I thought I would ask reddit haha and see if anybody has some helpful advice. My original plan was to do this in Colombia, mainly for the sake of cheap flights, but after some digging I found I could go to Barcelona for about the same price, which has opened a lot of doors for me. I was concerned about safety and fitting in in Colombia so this is great news to have more options. And for Thailand which is another place ive heard is great, the flight is 2x expensive but the day to day costs are half as expensive so im guessing it would even out. From there, I dont really know where to go to decide. If anybody has personal experiences to draw upon I would love to hear. Im concerned about being the youngest person in any crowd Im in and also not being able to meet people, Im comfortable with being by myself but recently im craving more social experiences. So whichever destination would provide better in that regard would be a benefit. Apologies for how long this is and thanks!