I read that Florida in North was a Spanish colony during Spanish colonisation of Americas. And also that USA helped other colonies to gain Independence. So was USA not under Spanish rule? If not why? And also if USA was under British rule so how come Spainiards were first to discover Americas? if they were first so they ideally should have ruled US.
Florida was discovered by Juan Ponce de León in 1513 and settled in the XVI century. In the earlier days of the Spanish colonisation of the Americas, it was ruled from Cuba. However, as time marched on, and bureaucratisation of the government of the Indies progressed, the Spanish America was divided into two viceroyalties (New Spain, and Perú). Florida was governed by the Viceroyalty of the New Spain, as was the rest of the Spanish North America (México, Central America, a big chunk of the present day United States).
At some point, the Spanish stopped venturing farther North because the logistics for it were astronomical in cost: they would have to establish new capitanías generales, civil governors, Audiencias (regional courts of justice), moving civil servants there, establish ground control, etc. Colonising that part of America was not seen as a profitable enterprise, especially considering that they already controlled the excedingly rich México with its silver mines, and the Fleet system that allowed them to tarde with Japan and China vía the Acapulco galleon.
I am just giving that answer from memory. When I get home I may be able to give you some sources, especially the 1783 letter from the Count of Aranda to King Charles III where the man explains why the recently born USA were going to support the other colonies potential independences, unless Charles did something as son as posible. To be exacta, Aranda suggested Charles claim the title of Emperor, establish some close relatives as Kings of México, Perú, and New Granada, and have a strong alliance based on the Kings' blood ties to the metropolis.