re: Time machine allows you to go back in time. The one caveat is simple ....

I would put clearer language into the expansion clauses (inter-state commerce and necessary & proper clauses), put in clearer language protecting the 1st amendment, and attempt to use my knowledge of the future to convince southern delegates to agree to a sunset clause on slavery, where after a certain date, the children of slaves are no longer slaves, but full citizens once they turn 18, and a ban on slave importation after a certain date, with the hopes of politically preventing both the Civil War and the disastrous presidencies of Abraham Lincoln, Andrew Johnson, and U.S. Grant.

Basically, I could use my knowledge of the future to close the wiggle room that lawyers, judges, and our government have used in the past to expand its power like Civil Forfeiture, civil rights, popular sovereignty, imminent domain, marshal law, voter fraud, regulation of utilities, public sector unions, ect.

If I can correct all of the grey areas to make the Federal government smaller, more free, and more efficient, while still giving it teeth to prevent states from abusing the rights of their citizens, I feel like I could prevent many of the issues we face today as a nation.