Update : Our flight was from Sydney -> Houston -> 90 mins layover -> Detroit. We used the Mobile Passport app and uploaded our pictures and passport information about 2 hours before landing. Once I had wifi and Cell data I clicked on Submit to get the QR code in the app. It took about 4 tries. I was about ready to give up thinking maybe our pictures were unrecognizable or something else. It went thru after the 4th try so do keep trying on your Mobile passport app if it errors the first couple of times. This was a huge time saver as there was nobody ahead of us in the Mobile Passport line for customs. We then proceeded to collect our bags which took about 15-20 mins. Once we got our bags we went into the connecting flights area and rechecked in our bags. Those guys were pretty fast. We then walked from terminal E to C and made it with about 15 mins to spare. Thank you all for answering my questions and all the help.