I'm not even sure if I understand this well enough, but it seems to me that this clause (see the [Wikipedia page] (http://en.wikipedia.org/wiki/Treaty_of_Paris_(1783)) demands that the United States not acquire any new territories after the treaty was signed. Was this ever somehow enforced? Am I missing something? The US did start their "era of Imperialism" relatively soon afterwards, did it not? What changed?
As the name indicates the Treaty of Paris was signed in Paris. To get information from the 13 Colonies to Paris took between 20 and 40 days depending on season and weather. The return voyage took just as long. That's about 3 months time before The American Colonies would receive word that the war was over. The point of the statement is the borders as designated in the Treaty were official regardless of any military gains made during that 90 days.