Why Is The Song Spanish Eyes So Difficult To Sing?

Context: so I can't seem to find anyone talking about this specific song on YouTube & answering the same question instead all I could find was various people talking about Spanish eyes e.g. looks and a video titled why Portuguese people have Spanish eyes

But nothing about the song so I thought I'd ask here

Here are some links to different versions of the song about different videos so you know exactly which song I'm talking about

Also sidenote advice on how to get better at singing songs with high notes as a 2nd base singer or base singer in general, confidence and Stage Presence

https://youtu.be/enIdTGckjKs?si=j_IPL2Lksi3IxTDO

https://youtu.be/OUDmNENn4es?si=sO_J1-oNxpJV2CLs

https://youtu.be/D7nzMliqqmE?si=AbfgX93BAGmubGD0

https://youtu.be/4CZtR16GTb0?si=iR2wA9Ef78XWrW0Q