Would american government be more efficient if power were concentrated within a single branch of government?

Technically, yes.

Since in single power there is noone that could limit the power of the country's leader, all of the leader's decision can be implemented without any resistance. BUT THIS WOULD BE A VERY BAD IDEA, because single branch of the government is basically a dictatorship/tyrannical government.

because this was the year that the state of israel was formed