First of all, .startUpload got deprecated and you may want to switch to the newer method.
Second , it should be:
let url = "https://static.wixstatic.com/media/" + uploadedFiles.url.split('/')[3];//to convert it to external URL.
Third, keep in mind that this way you will have each image file twice: 1 the file that got uploaded via the upload button and a copy that you imported from the url.