I look at this in 2 ways:
1) if you want to go with what's working now (which is good short term but might not work long term)
@Fang Yu was 100% correct in the sense that one big website that addresses many countries puts you in direct competition with the big dogs that you almost guaranteed can't beat.
2) the other point that I'd like to make is that you're trying to do the right thing as google tells you to, but there will come a time when google will have no say in how people should treat their websites. Imagine a world without google (and without search engines in general)!
In such a world your main focus is to have a great website that helps people with their travel needs, and for such a scenario 1 domain that talks about all countries is the way to go since you don't have to waste money like a lunatic just to please a retarded AI.
Personally, given how atypical I like to think that I am, I would go with option 2 (even if only to spite google, if that's even possible). But more than spite, I would do it because this would be MY website, MY business, and I do whatever the hell I want with it and a random garbage american corporation should have no say in what I do with my sites. Someone should really teach these american corporations a lesson and put them in their place (beneath everyone else).
Yes, I might never rank in google, and yes, I might never make money with google, but I still wouldn't care. I have had 4-5 sites that I have renewed and kept live for over 6 years back in the day even though they weren't ranking in google, but I kept renewing them and keeping them live just because I wanted to stare at them and marvel in how pretty they were (I'm not joking). I am this kind of crazy when I set my mind to something... In the end, in January 2022 (so, exactly 3 years ago) I've sold them and got done with SEO, I ain't ruining my life and mental sanity to please an obscenely rich corporation (google) to make even more money. You should do the same too, without us - the people - none of these corporations would still be alive and their CEOs and share holders would struggle heavily to find their place in society since they're not good at anything except for accruing wealth into their own hands. In any normal society the communities and honest people should thrive, while the parasites be humbled and struggle to fit in. Unfortunately, we don't live in such a society, but - fortunately - we can create one if we all stop doing what we're told by the ultra rich and powerful and do with our lives what we want (humans are free beings, they should have to answer to NO ONE, for ANY reason if they comply with the only 1 rule that matters: whatever they do, whatever they think, they should never ever EVER as much as insult or harm a single fly, much less an animal, plant, or - worst of a ll - a human being, no matter how they look like or whether they're from Earth or from elsewhere)
But anyway, I'm starting to digress and getting into the realm of insanity, so let me get back to the topic on hand
As I said, what Fang Yu said is 100% correct and it's what will work for you. But who's to say that in a few weeks or months google won't shuffle the algo and SERPs again (like they've been doing constantly for the last 2-3 years) and your niche sites will stop working? This is a valid concern if you're in this for the long term, and if you must adapt to the changes that google makes few times a year i'm sure you agree that it's easier to work on 1 domain instead of 10 (or however many you'll end up having). Not to mention the renewal costs and the costs for SEO-ing all of your sites (content creation, site monitoring, link building and site promotion in general, etc)
That's why I would personally opt for 1 domain that encompasses all of the countries you wish to talk about. Sure, you will get into competition with the big dogs, but this only happens in google where these big companies have mastered the art of dominating the SERPs. But if you focus on other sources of traffic where people don't know yet how to dominate you have a better chance of positioning yourself as the authority and - once again - if you find such an opportunity I'm sure it will be easier to position yourself as an authority with an already authoritative domain instead of having to do it with 10 different domains.
And since there are risks to never rank in google regardless of what you do, why not ignore google completely and plan & design your site the way YOU want it to look like, not the way google wants you to design it so they can steal your content anyway and train their imbecile AI based on your hard work?
So, go with 1 domain, plan and design your site the way you want, ignore google completely and focus on other methods of getting traffic (social media, podcasts, forums, PPC, online directories, radio advertising, ezines, partnerships with local travel agencies, etc) and you will see that - in the end - when you're big and hard to ignore anymore, google will come to you like a cheap whore (figuratively speaking, of course) and rank you in their dying search engine regardless of what SEO you did or didn't do on your site, and regardless of how many SEO rules you've broken. When it comes to smelling money and opportunities nobody does it better than big "successful" companies that are nursed to the dollar and can sniff profits from the other side of the galaxy, so start thinking and acting like you're already a big dog in your industry and the results will follow regardless of what google thinks of you for now...
