Because once an indentured servants time is up, you have to let them live their own life, but if you have a slave, you literally own them and keep them until they die if you choose to do so.
He passed NAFTA (North American Free Trade Agreement)
Answer:
When one branch of government has more power than the others, it could be a really bad thing if they choose to abuse that power. This is why in the USA, there is a system of checks and balances to prevent that from happening.
By instituting limits on the power of the presidency, one single person cannot dictate everything in government. The executive, legislative and the judicial branch have a system to keep each other "in check".