If you're into cities and landmarks I don't understand your interest in the Gran Cranny. The canyon's all about Nature.
Las Vegas might be a disappointment, too, unless you like gambling and glitz. The "landmarks" -- pyramid, Eiffel tower, volcanoes, gondolas -- are all fake, and there's nothing there a European would consider "historic."
A proper tour itinerary needs to be tailored to your personal interests: Architecture, adventure sports, natural wonders, cuisine, &c.
You say you like cities. Do you like walking tours or prefer a bus? Do you like history or prefer clubbing? Museums? Music? Hanging out with natives?
By landmarks I mean natural scenery and man-made marvels.
As for Vegas, I don't gamble regularly but for places reknown for such things, I would budget an amount. Not to mention i'd love to see the shows at Vegas, the Caeser's/MGM, the dining,etc.
As for nightlife, i'd what you call a 'classy clubber' in that i'd go to international themed parties/ be happy sipping drinks early evening
I simply enjoy urban areas as long as there's either a beach or a landmark e.g I enjoyed NY due to Empire State/Chrysler/Statue of Liberty. Same applies for Shanghai and it's Pearl Tower, Financial building and Bund (though Beijing was much less polluted and crowded even though the layout was strange)
That's why I don't really like British cities; they're dull and most are actually covered up in the form of malls. I've been to 9 major cities in the UK and as you can see, I enjoy the bigger ones
London- the best so no complaints except price
Southampton- smaller than most cities but multicultural and lots of places to shop/eat. Nice nightlife
Birmingham- amazing but bad weather and bad transport
Manchester- same as Birmingham
Liverpool- bad weather and the only redeeming feature is the waterfront; ugly shopping centres.Southampton and London have better waterfronts
Winchester-bad road design and small
Nottingham-smaller than it looks and its shopping centres/nightlife suck. Town hall looks nice. Bad transport
Salisbury-small
Leeds- weird layout