You only have to log into NBC's app once across Apple devices:
It's much easier to fire up This is US and SNL on iPhones and iPads now that NBC's iOS app finally works with Apple's single sign-on (SSO). You simply have to activate the feature on your device by going to Settings > TV Provider and typing in your cable TV credentials to log into all the apps you have that support it. This update will sound even better if you have an Apple TV, since the network's tvOS application worked with SSO from the start.
See, the feature syncs across devices, as long as they use the same Apple ID. That means you only need to log in once on your phone, tablet or streaming box to access NBC's streamable shows on all of them. Neat trick, right? Unfortunately, you can only use the feature right now if you're in the US, since it involves collaborating pay TV companies. To see what apps have SSO support, head over to the App Store, select the Featured tab and find the icon that shows your cable provider's logo.