my three worries about going to America

I'm off to Las Vegas soon, for two weeks.  I have three worries:
1  tipping
2  using a knife and fork
3  my accent
I get so flustered and embarrassed over tipping, haven't a clue how to do it or when to do it.  In NZ, one only ever tips at high class restaurants.  I used to tip in taxis, now I don't even do that because the drivers seem to get highly upset by the gesture.
Here's a photo of two Las Vegas 'showgirls' who were standing in the Fremont Street Mall.  I thought they were there to entice folk into a nearby casino and I took their photo.  They bore down on me and demanded a tip.  I paid them.  One of the showgirls was an Australian.

I also get embarrassed over using a knife and fork because I eat the 'European' way, ie mashing everything onto the fork by aid of the knife, unlike the Americans who always look 'dainty' as they fork up their food, knife sitting on the edge of the plate.  I feel everyone in an American restaurant is looking at me and thinking I'm uncouth.  Mind you, I read that the reason food-choking is so high up the American scale for death is because they don't cut their food pieces small enough.

My last embarrassment?  I hate talking in shops, restaurants, to others when I'm in the States because my accent makes me stand out.  I always think I'm going to be 'ripped off' because of it.  Wish I could act out an American accent.