Tipping with service fee

Hi! I am a guest from New Zealand to the USA. Have tipped 20% everywhere because I a respectful guest and it seems like it is a cultural norm.

Flying to Las Vegas today- it seems they have a lot of "service fees" are added to bills. If a service fee is added, that is say 20%, is the culturally respectful thing to count that as the tip and leave no additional tip?

Note: I understand the view held by many that tipping is BS and businesses should include labour cost, I would never tip in NZ, but I am a guest in your country, and wish to be respectful one so do not feel the need to explain the why of how of tipping.