No Polynesian expansion as we know it.
That's actually pretty easy. The initial expansion seems to have involved small numbers. A plague, a typhoon or two, a massacre, and it doesn't happen. Let's kneecap the Lapita culture. They stay a fringy group occupying the sands and mangrove swamps along the edge of Melanesia, eventually dwindling to nothing. The Polynesian navigational package dies a-borning.
Now, the Melanesians are no dummies, and they were already all over the Bismarcks and Solomons 10,000 years before the first pot-spinning Lapita showed up. It's not hard to island-hop east from there. So, New Caledonia and Fiji still get settled, and so -- a bit further north -- does Palau. By 1500 AD they've gotten as far as Samoa. The rest of the Polynesian Triangle stays empty, though, as does Micronesia. We'll say nobody drifts west from South America, nor east from the Philippines to the Marianas.
[chews lip thoughtfully]
You know, it's surprising how little effect this has before the 18th century. I think the Enlightenment still comes up with the Noble Savage concept -- that drew on North America more than Polynesia.
This is a "no surfing" TL, which kinda sucks.
Other hand, birds! A couple of hundred different species, all extinct OTL. Everything from flightless owls to dinosaur-like 5-meter monsters in New Zealand. Also that monstrous super-eagle thing. Many will go extinct anyway when Europeans show up in force, but at least some should survive.
European colonization won't get going until the 19th century. Assuming European history is much the same as iOTL, it'll be almost entirely British: they have sixty years head start on the Americans, the French were never that interested in settler colonies in the Pacific, and the Dutch will have their hands full with Indonesia.
So, llittle British settler colonies on all the high islands -- Guam, Pohnpei, Hawaii, and of course New Zealand. Start as whaling stations, turn loose some cattle and pigs to run wild. After a while there are farmers. Export... copra, sandalwood from Hawaii, salt beef and hides. No sugar, or at least not at first -- too far from labor sources and markets. (OTL sugar didn't start catching on in the Pacific until the steamship-and-telegraph era.)
I'd expect the low islands and atolls to be settled much later; they're not going to be very attractive to 19th century Europeans, and while low islands are lovely, they can be quite challenging to live on. A rogue typhoon washes seawater over the whole atoll. Your crops got salted; everybody dies. A bad El Nino means the rainy season doesn't come this year; your cisterns didn't hold two years of fresh water, everybody dies. A shift in the currents makes the fish go away... you get the idea. I'd expect at least one Croatoan-style complete wipeout on an atoll somewhere.
So, half a dozen mini-New Zealands. Hawaii becomes a sort of warm Falkland Islands.
Hum.
Thoughts?
Doug M.