Hulu is United States only. It has never launched elsewhere, and the Hulu that exists in Japan is a separate company that licensed the name. Outside the US the app and the website show a message that the service is not available in your area, and inside the US it is one of the largest catalogues of current network television, next-day episodes and the FX, ABC and NBC back catalogues, plus its live TV tier.
A VPN gives a US address, which is the first of two things Hulu needs. The second is a US payment method or a US gift card to subscribe, because Hulu checks the billing country as well as the address. Existing subscribers travelling abroad only need the first: connect to a US server and sign in.
Hulu does watch for VPNs and shows a specific error about an anonymous proxy when it recognises an address. As with every streamer, the address is what is flagged, and another US city usually works. Hulu's live TV tier adds its own rule: it expects to see the account's home network from time to time, which a VPN does not satisfy.
GhostShield's four US cities, Los Angeles, Miami, New York and Palo Alto, are the servers to use.