Look at the chorus
The song is from the perspective of any/all the "kings" looking back at how their lives were lived (how their "vidas" were "viva'd"). Each verse could refer to one or more historical figures, Louis XIV/Napoleon/etc, but the song is not about any particular one. It's poetry not history. (And a "king" for this could be anyone who actually was a king or who just felt like they had it all.)
The chorus is important to understanding the song and starts with a focus one very important "king", in fact one often called the "King of Kings".
"I hear Jerusalem bells a-ringing.
Roman calvary choirs are singing."
Cavalry or Calvary? Mixing these two words up is a very common mistake because of metathesis. The Romans were known for their infantry legions not their cavalry, but the Romans did crucify Jesus on Calvary Hill in Jerusalem. (I know what the official lyrics say and I know how it's sung, but Google "Roman cavalry" and the first page you find will tell you "As Romans were never considered exceptionally good horsemen, and the role of the cavalry not as important in the Roman thought process, the Equitatus was generally made up of non-Roman horsemen." )
"Be my mirror my sword and shield"
My missionaries in a foreign field."
This directly echos the Bible (Ephesians) referring to "the sword of the Spirit, which is the word of God" and the "shield of faith". Jesus' disciples are his missionaries who he wants to "reflect" his message to the world even after he is gone.
But this is not a religious song as such. The second half of the chorus is more general about how those in power cannot trust the advice they receive nor can they be trusted to speak honestly themselves when looking to protect their power. And in the end, they will know if they have lived a life that would expect to be let into heaven for--and I think it's more about the feeling of the "king" looking back on how he now judges his own life not about whether Saint Peter would literally let him into heaven.
And it's one of my very favorite songs! Well done.