What is that? Across from what road??

I don't understand the question. It does not compute. Before Jesus died, there were no vampires or zombies. People came back from the dead routinely. No reason, they were not vampires or zombies or anything else in particular, they were hallucinations, religious skullduggery, entertainers, and scam artist tools. After Jesus died, it became well known and commonly accepted that the ONLY person who came back from the dead was Jesus, so when people continued to come back from the dead, they had to be called something else besides 'humans coming back from the dead'.

Do you guys know where I can get one of those gold necklaces with a "T" on it?
That's a cross.
Across from where?
- I pity the fool.

I enjoy the Castlevania show interpretation of vampires being evolved predators and a large geometric shape being shoved into their vision causes them to freak out. Kinda like a cat seeing a cucumber.
- I'd be ok with it if they were like zombies or something, but they're intelligent so that explanation just feels like such a stretch to me. Are vampires also affected by window muntins and fences? Can I fend off a vampire attack with a suit of graph paper armour? Do they freak out at the sight of jungle gyms?
  
  Are vampires also affected by window muntins and fences?
  Yes, that's why they need an invitation to get on your property
  
  I mean, if you shoved a jungle gym in my face I would probably have an issue with it.
  As a practical similarity, ever heard of speech-jamming? The idea is that you can play someone's own voice back to them with a slight delay and it will cause them try and listen and speak at the same time resulting in slower speaking or even the inability to speak normally.
  I feel like a vampire could have unique instincts or mental processes that could be messed with in a similar way. Maybe it's like how people can see faces in very simple shapes; they see threats instead.
  ; - )
  
  but they're intelligent so that explanation just feels like such a stretch to me.
  I'm intelligent, but you can still ward me off with christian rock
- They straight stole that from Peter Watt's Blindsight. He has a doctorate in biology and really fleshed out the backstory on how vampires evolved.
- I version I read in a book (can't remember that name of it) was whatever religus artifacts the vampire had faith in whould be the what hurt them, (Star of David hurting a Jewish vampire)
  
  https://youtu.be/RdeG58J2kbE
- Castlevania vampires would just explode in Reign: The Conquerer. The show where the whole plot was about looking for a literal magic shape.

Also, does this work on other vampires, or only those from European origins? How does this effect the greater vampire populace?
If others aren't affected, what's stopping another type like Jiangshi from taking over new territory?
(Going with Jiangshi purely because they're the first ones to come to my mind when thinking of a "non-typical" vampire for part of the world).
- According to Trevor Belmont it's not the religious association that's effective is the bold right angles blocking out their vision because they're predatory and they have tunnel vision, I guess. So it blocks their sight in a way that's disruptive. That's the Anime at least. Honestly it sounds very stupid, to me it would make a lot more sense to say holy items aren't effective against vampires because of anything to do with vampires, but due to the beliefs of the one using holy items, so it's their personal faith that gives it power, which at least makes some kind of logical sense. In a magic world the magic user provides the effects not the target.
  
  The same thing happens in blindsight by Peter watts. Perpendicular angles cause seizures in vampires
  
  I like to imagine that there's no divinity or anything like that, it's just that the vast majority of vampires fucking detest christians for one reason or another, and simply refuse to stick around when they see a crucifix.
  Some are so ancient that they spoke to mohammad and are devout muslims, some just predate christianity so consider it extremely stupid, some had bad experiences with the catholic church and don't care to distinguish sects, and some simply fell into the militant atheist rabbithole and unironically wear fedoras because obviously no one can stop them doing so.
- The cross is just a conduit of divinity, so the shape or type doesn't matter. Any creature harmed by divinity would be affected.
- I feel like other cultures predating Jesus would have had stories about humans who suck blood, and are undead. African cultures had zombies e.g. but that’s not quite the same thing. Probably South American like Mayans and Aztecs had similar myths. Though I’m guessing they probably didn’t turn into bats. Or does that concept also transcend cultural myths?
  Maybe vampires were unstoppable before Jesus. So not only did he save us from sin, he also saved us from vampires.

White Wolf vampires respond to strength of faith, and the symbols are just a means to express that faith.

This gets addressed in the book I Am Legand. In that, it's about the vampires religion and their feelings about themselves. Same with mirrors.
- How do mirrors feel about themselves?
  
  Ha!

https://youtu.be/VTF2-5mnCN0

https://youtu.be/HAom8ws8qp4