Do you have any suggestions for when visiting USA? (west coast)

I'm going to San Fransisco-Vegas-Los Angeles over christmas and new years and I have never been in USA before. Does anyone have any tips on restaurants, places to visit, anything in these cities or nearby?

If you have any special place you like I wanna hear about it!

It's not any of those, but doing the coastal drive across the Big SuR between San Francisco and LA is absolutely essential. I did it with in 2014 and it remains one of my favourite US memories. I'm not super sure about the weather for it over Christmas though.

We had already planned going through Big Sur! Sounds good!

Honestly the big thing is food. LA has some amazing and affordable cuisines, particularly Mexican and East Asian - obviously your mileage on this front will depend on your food experiences from home, but if you're not all that familiar with this sort of variety, I'd almost say shoot for that over anything typically "American." One of my favorite eating experiences in LA was following some of the places listed here. If you've never had Dim Sum, I can't recommend it enough. You'll have good options for it in both SF and LA.

If you're a fan of science museums, the Exploratorium in SF is hands-down my favorite. The California Academy of Sciences is also fun, but focuses less on hands-on physics stuff and more on the nature/biology side (although the biology exhibits at the Exploratorium were super cool last I went). I'll also give a shout-out to the California Science Center in LA, where my brother-in-law works. They have some phenomenal aerospace exhibits there (I got to see the Space Shuttle when I went) and a great team of volunteers who will happily answer your questions.

If you like hikes/nature/whatever, Point Reyes is a real good option in the Bay Area.

Oh, and if you make it to the Exploratorium, the TCHO chocolate factory is nearby, and they're by far my preferred SF-based chocolatier (Ghirardelli doesn't really do much for me, Guittard is a far better workhorse brand, and neither holds a candle to TCHO IMO, but that'll be reflected in the price so *shrugs*)

Take a look at this map. Watch out for poop!