Because the letter 'V' is a voiced fricative US'ns would *naturally put a vowel between a 'V' and a 'T' when spelling out a pronounciation.

I wonder if of troy would agree with that.

Um...I think where you put the emPHAsis (hi, tsuwm) makes a difference. I never say or think OF troy--it's always of TROY, so I have no "need" of adding a sound in there. But the music is pol-OV-tsi-an, and it's easier for English-speaking tongues to say pol-oh-VET-si-an. I think.