Gender dysphoria is a mental illness that can occur in anyone, regardless of culture. Every culture has gender roles. Inevitably there will always be people that identify with the opposite gender they were assigned at birth.

Western transgenderism says that people are somehow born in a body that does not match their internal map of their body and that this causes them distress. This was not the case traditionally for fa'afafine in Samoa, for example.

It is perfectly possible that gender dysphoria is a product of Western culture and influence, in the same way that in some cultures men sometimes become convinced that their penis is shrinking.

Transgender people have been around for forever. They were simply erased from history.

How super convenient for your argument.

This is like claiming that Greece was full of gay men. It is true that men in Ancient Greece often had sex with other men, but they perceived what they were doing differently from gay men in 2022 America. Their homosexual activity was usually dominant older men penetrating younger boys. It was the penetrated-penetrating difference that mattered to them, not homosexual vs. heterosexual. Likewise, different cultures at different times have had different approaches towards third-genders.