The Spanish Acquiesced To The British

From The Mississippi Valley historical review (1914):

Plans for the capture of these Spanish possessions in the event of war were fully discussed by British authorities. The two countries seemed on the verge of war in 1770 on account of the dispute over the Falkland islands, and General Gage, commander of the British forces in America, was ordered to take steps preparatory to an attack on New Orleans. With the ultimate capture of the entire province of Louisiana in mind, mobilization of troops at New York was begun early in 1771. But the king of Spain, before hostilities were actually opened, acquiesced to the terms submitted by Great Britain.

What happened earlier:

"In 1763 a treaty between France, Spain and Great Britain was signed at Paris, which terminated the seven years war (called in this country the French and Indian war), and under its provisions there was a complete redistribution of territory in the South and West. Louisiana, which then included the Isle of Orleans and all the territory west of the Mississippi, was ceded to Spain, while Florida, extending from the Atlantic to the Mississippi, and including all the territory on the east bank north of the Isle of Orleans, was given to Great Britain as the result of the glorious war...".  [Source]