The cross border costs is mainly the exchange risk surely, plus the compliance risk (I call it the OECD shit, they dumped liability onto their banks, so the banks in turn, choked off a lot of their transaction economy rather than assume the risk).
Given the actual transmission and verification can be done by computers, the transaction itself isn't the delay, and the exchange risk is simply because the banks chose to add that delay to their systems. The exchange rate may vary between the time of the transaction and the actual processing, of the transfer. That risk is priced into the exchange spread, plus they get to add their profits ontop hidden amount the large exchange spread.
Crypto crapto doesn't fix any real problem here. If anything the number of scams and thefts show it's got more attack points than a centralized system. A centralized system needs a central currency. What currency would be the core one in that case? SGD? Renmibis? Rand()? Ponzi Coins?
Imagine the world largest manufacturing economy, China, offering bank accounts in CNY. Anyone can open an account, you transfer money in, it stays in CNY, you buy your Chinese goods direct from China, paying from your own CNY account, access it using Unionpay, you invest in the Chinese stock markets, in CNY. Gone is your exchange risk. No OECD shit too, that's a European/US thing, Asia hasn't mawled their banking system the way the Euro was mawled.
That could once have been the Euro, that use to be the dollar.