Two years ago, Jacob Helberg, a little-known tech industry adviser, convened a dinner between lawmakers and a small group of Silicon Valley insiders on Washington’s Embassy Row. Funded in part by billionaire investor Peter Thiel’s venture firm, the group was not distinctive for its wealth or clout — the people involved had plenty of both — but for its members’ eagerness to eschew the industry’s long-held ideals of boundaryless technology for an alternative vision rooted in American nationalism and an anti-China might.