I've been skiing in the US and loved it every time. The base is always massive, grooming excellent, queuing is polite and efficient and pistes uncrowded. Relatively, on-piste eating is cheaper then the Alps. Hotels I've stayed in have a ski concierge who stores and waxes your skis overnight and there's a wider choice of accomodation.
BUT equipment hire, passes and accomodation are relatively expensive. There's always the worry of being sued after an accident. And pistes can be binary - either wide open intermediate or impossible double-diamond, with less of the difficult reds/easier blacks that you get in the Alps. And I don't think that I will ever understand why their chairlifts
lack restraining bars, given the American preoccupation with safety.
However, I've only skied in the USA because I was already there on a business trip or training and able to tack skiing onto the end. I wouldn't endure the long-haul flight plus transfer (e.g.
Lake Tahoe is fantastic, but it's an 11-hour flight to
San Francisco then a 5 hour drive) - and definitely not for just a week's skiing.
If you have youngsters along, then I'd echo the post that said the Italians are very child-friendly. All three of our children learned in
Livigno and the instructors were great. Switzerland instruction was also good, but obviously, the trip was more expensive than Italy.