Is hosting the back end in the cloud supposed to significantly slow performance? I moved my back-end from a local .accdb source to Microsoft's online Access App. Ever since then, forms have been taking more than 20 times longer to load. Is this normal? Or is there something wrong with my connection?

I'm using Access 2013.
Well, if the backend is sitting on an external server, your network speed now plays a major part in the connection. Accessing local files off harddisk is fast, but accessing it of an internet connection is slower. 

Try testing your app using a faster internet connection and see if there are differences. If there are minimal differences, then it could be the server hosting your app that is slowing it down. But my main bet will be the internet.