React cannot read properties of undefined inside conditional statement

Question

I'm fetching data from an API which returns an object that looks like this.

results: { 
    AT: {
          buy[],
          rent[]
},
    US: {
          buy[],
          rent[]}
}

And I'm having trouble checking whether the property US exists. This is resulting in a cannot read properties of undefined error. The way I'm attempting to do it looks like this.

{typeof(provider?.results.US.flatrate) !== undefined && provider?.results.US.flatrate.map()}

The data is stored inside provider using the useState hook.

const [provider, setProvider] = useState<Monetization>();

The way I'm fetching data from the API looks like this.

axios.get("https://api.themoviedb.org/3/movie/" + movieId +
            "/watch/providers?api_key=my_key").then(res => setProvider(res.data));