Is possible to call async function without await keyword? and what happens if we call without await?

You only need await if the caller needs to wait for the function to be done, for instance when it needs the result of the function, or when it needs to wait for some state/data change that the function causes. If there is no such dependency, you can just 'fire and forget', by not using the await keyword.

As others mentioned, you could use .then as well, but the basic rule is the same: you do that, when you have something specific to do after the function is done. It can be omitted otherwise.

So concretely: With 'caller', I simply mean the function that calls the async function. In your case that would be componentDidMount. The options are then quite simple:

1. Keep as is. usrs() will be run in the background completely and componentDidMount will continue running until its end.
2. Use await, so componentDidMount will wait for the return of usrs().
3. Use usrs().then(), so componentDidMount can continue, but the code specified in .then() is invoked after usrs() returns, if you need to do something that has to happen after usrs() is done.

We use await when we need to call and wait for async function or Promise
In your case when you call it without await inside your componentDidMount, your function will work but your componentDidMount will not wait for that function to completely finishes.
Also if you don't want to use await and you don't want to wait inside componentDidMount, but you want to get notified when your async function finishes, you can use .then instead. Because async functions returns Promise

Here is your componentDidMount with .then
Notice that in this example this.doSomethingElse will call before the this.usrs is complete, and you only will be notified inside .then about your this.usrs result when it finished:

componentDidMount(){
    this.usrs(usrs).then(() => {
        // Your functions completely finished
    })
    .catch(err => {
        // There was an error
    });

    this.doSomethingElse();
}

The async work before the name of the function means that the function always returns a promise, so yes it is possible.

await makes JavaScript wait until the promise is resolved and it pauses when you need to work on the result of that promise.

To understand it better I recommend seeing following page https://javascript.info/async-await