Why did americans fear a strong national government?

Because they could take away the power the people have

The Declaration of Independence starts "We the People" not We the Government. The Government is their to protect us from foreign threats and to enforce the constitution which they are destroying with every passing presidency. They can't handle the resposibilities they already have, why on earth would the people want to entrust those incompetent fools with any more.        

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

producing or giving rise torelating to or engaged in the production of goods, crops, or other commodities.

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.