The viewers votes have always been poitical but you would expect allies to support each other. Apart from the UK and Ireland seemingly! Other than that, no, it is pretty non-partisan.

As to the performances, well, yes. The performance of a song can be of equal importance to the song itself in terms of enjoyment. Why else have live performances if not for the visual impact as well as the music? If you want to hear perfect music, listen to a rcording. If you want all senses stimulating, go to a live performance. Horses for courses!