I'd go one step further and say that, sure, all politics are local--if you're Tip O'Neill and represent a ironclad Democratic seat in Congress. It's easy to be smug about your political skills if you're in a safe seat and have enough pull in state politics to avoid your district getting gerrymandered. Then you can sit there and sagely attribute your success to your continuing mastery of local politics rather than to whatever it took to get the seat in the first place.Yes, but: don't most Members of the House have ironclad partisan districts? And isn't the most important single thing they can do to protect themselves involve having pull in state politics to avoid being gerrymandered? That is "all politics is local," no?
There's also a fair amount they can do to stay on the good side of their local party, thus avoiding a primary fight. And, even in an era of nationalized elections, there's still plenty a Member of Congress can do to to influence elections on the margins, and that's often what matters.
Sure, "all" politics isn't that stuff, but it's quite a bit. If I were a Member of Congress and had the choice between (A) controlling national tides, and (B) controlling my state's redistricting, then I'm going to choose B every time -- and that's in O'Neill's column.