What are two similarities between the United States constitution and the constitution of the confederate states of the America?

They both had a form of federal government, even though there was more "state power" in the Confederate States, as noted in the Confederate preamble.

The Confederate document was basically a copy of the US Constitution, except for some pointed changes: the term of the president was 6 years, bills in Congress were restricted from having non-germane amendments, and (pointedly) industry could not be supported by tariffs.