Niseko used to be notoriously painful to reach, an isolated corner of rural Japan, but things are most certainly on the up! Sapporo (札幌) is the nearest city to the resort, with the New Chitose Airport (新千歳空港) cleverly positioned to receive the least snowfall and keep flights running smoothly. Your most likely route from the majority of US cities is going to be to via Tokyo, but direct flights to Sapporo do run from Honolulu, Seoul, Taipei, and Hong Kong, so those routes could be worth considering too. As for transport from the airport to Niseko, you've got a whole bunch of options...
A simple and economical way to get you and your gear to the bottom of the mountain is a trusty shuttle bus. A ticket will set you back around 3,000 JPY, that's one-way, plus you can expect wide comfortable seats and a bathroom stop if you forget to go before climbing aboard! Buses run every hour during high season, starting at 9:30am up until 9:30pm, and usually only 80% of the seats are ever taken.
Tickets can be easily bought at the airport and travel times depend on which of the ski villages you're staying in. First stop is Annupuri after two hours, next up is Niseko Village at two and a half hours, and finally you'll reach Hirafu after three hours. There are key stops in each of the villages, dotted close to the clusters of tourist accommodation, so most of the time you can simply walk to where you're staying. That said, it's worth checking beforehand whether you're staying far from the bus stop or not.
Japan has great trains, so why not take one! You'll actually need to take two, which makes this mode of transport less convenient and more time-consuming than a shuttle bus, but it's there if you want it. From New Chitose Airport Station take the JR Rapid Airport line to Otaru Station, where you'll change to the Hakodate Honsen line to reach Niseko Station. A one-way ticket will set you back around 3,500 JPY, and the whole journey is likely to take three to three and a half hours depending on how long you have to wait for your connection.
If you're traveling as a group or family then perhaps a private taxi takes your fancy, it's a bit quicker and you won't have to wait around for the bus or train, but it'll set you back a minimum of 26,000 JPY. That's just for a basic car to fit four people, for larger cars and people carrier type vehicles the price can go as high as 50,000 JPY. Still, you'll get dropped off at the door of your new home in Niseko and it shouldn't take much longer than two hours to get there. Don't wait until you're at the airport to organize this, book online at Niseko Shuttle Bus.
The ultimate in flexibility but the most painful in price, hiring your own car means having the freedom to explore the different ski villages in Niseko, particularly Moiwa. However, think twice about driving here if you're not used to icy roads. In fact, don't think about it at all, just take one of the other options we've just mentioned. Confident behind the wheel in slippery conditions? Great, but you'll still need to get your International Driving Permit from the American Automobile Association before you leave.
Cost wise, expect to pay 90,000 JPY per week for a car like a Corolla, and factor in another 6,000 JPY for toll roads. It's worth getting the ski racks, an optional extra but undoubtedly handy on a ski holiday! Forget the snow chains unless you don't feel comfortable without them, your car will be fitted with winter tires which will generally do the job just fine.
One more thing, don't bother hiring a GPS, unless you understand Japanese you'll struggle to use it (to input a destination, phone numbers are used instead of addresses). Just make sure you have Google Maps downloaded and make the necessary arrangements to have data available on your phone. On the plus side, all the villages have free parking close to the lifts and they are rarely full, so at least you won't get a ticket! Book your wheels online, pick your ride up at the airport, and expect a two-hour drive to reach the mountain.