Are you in the UK, or another country? In some places, cancelling or not turning up last minute isn't considered to be particularly rude or offensive (and of course in other places it's unthinkably rude, and in most places it's a bit off, but, still...).
The hurtful thing is that, yes, the odds are that your friends are either a) assholes (who doesn't even call to cancel?), or b) they consider you a peripheral friend, and their arrangements with you to be fairly inconsequential. Not in a nasty way: just, meh, if I make it that'll be nice, but I won't put myself out. This is not your fault.
Feeling like you never move beyond acquaintance status is one of the hardest things about relocating as an adult. It seems like everyone around you has a core group of old friendships, and they probably assume you do, too, so you get lots of superficial contact but there's nobody you can 100% count on.
It does get better, but it's so slow. Before I lived overseas, I used to be quite snobby about people who socialised with lots of other expats: why would you move halfway across the world and only hang out with the kind of people you already knew at home? But now I get it. You get so tired of feeling like you'll never quite break through and nobody's got your back. So be kind to yourself and definitely don't get into self-criticism and self-doubt.
Although, yes, I'd probably give the no-show people one more strike and then they're out - even if they somehow assumed you'd have a million other people to hang out with, it's rude to stand you up. Actually, that's another difficulty about navigating international friendships: it sometimes takes you a while to understand that this isn't a cultural difference and someone's just being a twat.