The Roosevelt Corollary was a revision to the Monroe Doctrine.
In 1904, Roosevelt decided to conform to former <em>Monroe Doctrine</em>. The corollary was a foreign policy by which the United States will intervene in any conflict between <em>European countries</em> and<em> Latin American countries.</em> This will insure that European claims over Latin American countries will be legitimate and will avoid having the European claims directly.
The three most important problems was that it gave to much power to the states (weak central government), it did not give the federal government the power to tax, and congress couldn't regulate trade.
Answer:
National defence and Social security
It was used to foul the rapidly increasing motorized vehicles
