Bob
You are right those olden links courses did undergo change, you can add Hoylake, Westward Ho!, Sandwich, Birkdale, County Down and even the Old Course.
A look at the early courses that hosted the US Open and Amateur, presumably the cream of the crop: Newport, Shinnecock, Chicago, Myopia, Baltimore, Garden City, Baltusrol, Glen View, Onwentsia, Philadelphia Cricket, Englewood, CC of Buffalo, Brookline, CC of Atlantic City, Nassau, Apawamis, Ekwanok, CC of Detroit, Merion. Most of these courses were altered, many significantly, and of the eighteen courses, nine were replaced completely...the old course being NLE. Pebble Beach, Columbia, Pinehurst #2, and Oakmont were revamped as well.
Huntercombe, Swinley Forest, Addington, Worplesdon, Stoke Poges, St. Georges Hill, Walton Heath, West Hill, Royal Ashdown Forest, Coombe Hill and Alwoodley were more or less kept intact during that same period; many of them are surprisingly close to their original form today. I think the British are pretty cheap when it comes to golf, Americans have never had any trouble throwing money at their courses....with mixed results from an architectural point of view.