Absolutely not. Like Iraq, Liberia poses no compelling threat to America or it's interets. As far as I am aware no mutual defence treaty exists between Liberia and the US. And there is frankly no evidence that the US would not botch it as badly as they have so many other countries' "liberations."
Just because you can kick someone's ass does not mean you can solve his problems. Just because you have more money than someone does mean you can solve his problems. If the people of Liberia cannot or (more likely) will not help themselves, there is no reason on earth why the US or anyone else should.
If the UN is so hell-bent on helping Liberia, they should consider lifting the assorted embargos that they have enforced on the nation (diamonds, travel, and -- ironically -- military support.)
Liberia is a country literally dying from neglect -- the infant mortality rate is in the double digits and the average life expectancy is just over 50. The migration rate is consistenly negative, with approximately 1% of the population leaving the country annually.
This is a country which has slid so ar backwards that even what precious little progress they have made is destroyed in a futile attempt to reverse the downward spiral: out of three rail lines in the country, none are running as the state has long snce sold off the trains and even part of the tracks as scrap. Yet like most backwards, shitwater nations, Liberia abounds with resources that are either untouched, or exploited by the corrupt political and military classes.
Given the above, which are facts seperate form any philosophic or political argument, simple facts and statistics -- would you live like that? Would you sit back and watch your country just disintegrate over a period of decades, watching your condition worsen to medeival levels while most of the rest of the world prospered? If you would -- and that's pretty much all that's left in Liberia, people who would -- then you deserve exactly what is happening in Liberia, as it is the logical conclusion to a sorry history.
Phaedrus