Javascript: Cannot Read Properties of Undefined

Question

I am getting this error when trying to run the code below (I am using the script editor in Airtable for those familiar). The API output is an XML string that I am converting to an object with some code I found on Github.

let response = await fetch('https://myapiendpoint.com/parameters', 

{
    method: 'GET',
    headers: {
        'apikey': 'MY KEY'
    },
})

let myResponse = parseXML(await response.text())

console.log(myResponse)
console.log(Object.keys(myResponse))
console.log(myResponse.Users.User.FirstName)

Console Log

You can see that even though I am using the correct key, I am still getting an error when trying to call the FirstName key from the third console.log line.

Any assistance would be greatly appreciated