If a restaurant raised it's prices to encompass the increase in wages, a certain amount of the dining public would look at it as too expensive to eat there on a regular basis. What percentage that would be would determine if the restaurant survives.
The note of "20% across the board" would not be too abhorrent unless that also included bottles of wine etc... a $250 bottle becoming $300 or worse a $500 one now costs $600!
As far as differences in tipping culture, I would follow the when in Rome model. You can ..... about it but you better watch out for the dog poop while in Paris. How about the peeing planters in Paris? Vive La difference!
I guess some of this thought is derived from working at some fairly high end restaurants in DC while in school there and making a decent amount but also dealing with a fair amount of tourist diners who I honestly have to say, we approached with trepidation when it came to tipping.