"Intervene" is a bit of a cover word. Does it mean giving them aid? Invading? toppling their governments? Because the US has resources, does that require them to come to the rescue?
If the US, or any country truly wants to help another, the best, only and most effective activity would be to trade. Mexico, for example, has a supply of oil; the US has a huge demand. By trading, wouldn't that be benfitting the people of Mexico and the US?
Trade can only function where there is political stability, and stability can only be achieved when there's minimal corruption in the government and maximal freedom for individuals to pursue their various business interests.
Are the problems in Central America from their own internal difficulties, or undue (and unjust) political influences from the US?