The United States has not used a formal naval blockade since the Cuban missile crisis of 1962; although blockades were used during the Gulf War of 1990-1991, this was part of the overall war strategy to defeat Iraq and not a separate action without ground troops. The United States has the largest navy in the world in both the sense of ships and of personnel and can easily afford to deploy that naval knowhow, manpower, and its various naval ships to any area of the world to effect necessary change, if required or designated to do so.
Although the USA is a signatory to numerous treaties and agreements, it is also a nation that is not afraid to go it alone, or to stretch the legal meaning of words, to accomplish whatever it believes is necessary to be done in the world at large. One of the primary mistakes that America has made over the last fifty years is not recognizing the power of its Navy and the effectiveness of a blockade that limits both the exporting and the importing of goods within the subject country that the United States wishes to apply pressure to. More times than not, patience and an economic squeeze are just as effective as the actual engaging of ground troops against enemies but with far less peripheral damage.
In today's world, exporting and importing of goods is absolutely essential for virtually any country of substance, because of the vital materials that are being shipped in by sea, such as oil, steel, fertilizers, machinery, chemicals, and electronic equipment. As for whatever a particular country is exporting, if they aren't able to export it via sea, in a lot of cases, they won't be able to readily export that particular product and without those essential revenues the whole country apparatus will begin to slowly fall apart.
While there are attendant risks to any blockade, there are few countries that will risk escalating the situation to an all-out war with America, while suffering from the stranglehold of an effective naval blockade. Another advantage of naval blockades is it allows both parties in a dispute an easier avenue to remedy a situation before it gets entirely out-of-hand. Saving lives on both sides of an altercation should be of primary concern to all civil nations and for the United States to have any moral suasion in this world it must lead by example and therefore it should show mature restraint in its disputes as opposed to the iron fist.
In general, the American public will not long support ongoing military engagements with perceived enemies for whatever the reason , unless we as a country are in immediate peril or the world-at-large is staggering to Armageddon. Naval blockades allow America to get into that "sweet spot" in which they can still apply necessary pressure against rogue nations without the unnecessary cost and bloodshed that a war entails.
Well thought out naval blockades in conjunction with specific embargoes are extremely effective in bringing forth a result that will bring unprincipled nations to the negotiating table. While blockades are a slower process as compared to unleashing the "dogs of war" it's also a more tolerant and forgiving way to deal with nations that have erred.