Diploma certificates don't normally need to be uploaded and will be specifically asked for when needed. The transcript should be sufficient in all cases as it should show the awarding of the degree and any honors attached.
In the rare case that the transcript doesn't show the degree awarded you might be asked for more, but if you are asked late in the process the normal deadlines won't apply as long as you are prompt.
Relax, and just submit what is asked for. The US system may be different in many ways from the one you are most familiar with.
For the benefit of future readers, other certificates, such as those given for some online courses, aren't required either and probably wouldn't be considered even if sent.