Which modern president had the biggest impact on America?

Although it's not a popular answer I would have to say George bush jr.

Explanation:

Bush was president under a difficult time in america one of the most difficult since the coronavirus pandemic. His actions during 9/11 created Homeland security and the TSA forever changing the way the state allows it's own citecin to move out of the country and arguably stamps on humans ability to movement into and out of country and the deepening of the surveillance state.

Abraham Lincoln

Explanation:

Its obvious.. :\

the us constitution is a living document, meaning that it can be changed over time as the country changes.