Over the course of time, the inherent weaknesses of the Articles of Confederation were cruelly laid bare as America developed both as a trading nation and as an international power. However, there can also be no doubt that the Articles contributed in the long run to America's preeminence in both these crucial areas.
First of all, the Articles of Confederation allowed America to fight and, ultimately, win the war against the British. The Articles provided America with a unified government of the colonies which allowed them to be a much more effective fighting force. The federal governmental structure under the Articles was (deliberately) weak, but a sense of unity still prevailed between the states as they came together, not through centralized compulsion, but through a shared commitment to liberty. Sustaining and maintaining this radical notion of republican liberty was undoubtedly an achievement of the Articles, one whose spirit still lives on today.
This lead to another major achievement. As the Articles were forged in the cauldron of war, Americans came to reflect on what changes needed to be made to the nation's governance. In other words, the Articles helped pave the way towards the provisions of the Constitution. Although the loose governmental structure had enabled the United States to win the war, it soon became clear that significant changes needed to be made if the new nation were to establish itself on the international stage.
Finally, the Articles of Confederation established a process whereby new territories in the west could be admitted into the United States. This mechanism allowed the relatively speedy resolution of territorial disputes that otherwise would have threatened to rip the new nation apart. This process culminated in the Northwest Ordinance of 1787, which was of great strategic value; it greatly strengthened the United States against any possible future incursions by hostile foreign powers because, as a result, there was now considerably more land and people to conquer and subdue.
Indeed, it is noteworthy that even after the Constitution replaced the Articles of Confederation, Congress enshrined the Northwest Ordinance as law, retaining what was undoubtedly the Articles' most significant and lasting achievement.