Strong military leadership and support.
Federal government is the result of a union of states. Which, could be assumed not to be sovereign. Unitary Government is when there are no states in federation, rather the government is all (other than local needs) at national level. Thus Unitary is not Sovereign.
The similarities between unitary and federal states could be that both types of governments could be democracies. A unitary state could be democratic when the people elect the government officials, as is the case in a federal state.
Probably the best country to fit this mold would be ISRAEL, but Cyprus, Lebanon, Turkey, and Iraq could fit this description with some caveats.
republic _____ No, unitary, or centralised. A kingdom, duchy etc could just as easily fit the description in the question.
The short answer is that if the united states became a unitary state it would no longer be "united states" but rather the "united state." Perhaps some successor state occupying a portion of what was once the US could be a unitary state, but the likelihood of all the constitute parts of the US voluntarily relinquishing their legislative and administrative prerogative is minute.
It is possible, it could happen in any country.
Dictatorship
That is not the correct quote. John F. Kennedy said "Ask not what your country can do for you, but what you can do for your country."
Chaos and anarchy are a possibility.
Your country could get kicked out of the European Union if you were voted out. More than likely this won't happen though.
Yes, Togo is a very stable country but the government isn't the best it could be.
Unitary gov. all the power in the government is held by the central government (China and Japan)!