Assuming they were not struck dead by future shock (photo, radio, television, telephone, mobile handsets), they would lose their damn minds that Black people have escaped slavery, non-landholders can usually vote, and the Presidency is (mostly) determined by the popular vote.

I do not think any of the founders, however amorphously the term is applied, would have interesting thoughts about cryptosystems for the examination of private photographs stored in commercial cloud setups.

They would die promptly from any of a number of diseases common to us that they have no natural immunity to.