IMHO you far overstate the actual strategic importance of Florida; the Spanish captured it as an afterthought (well, that and to defend their northern flank in the Carribean), and when the British did have it it had failed to play an important role...
So I doubt that it would have a really major influence on the 17th and 18th centuries, much less the 16th; there might be some local changes, but probably not enough to seriously affect the geopolitics of the time period.
Now, in the 19th century things get more interesting. I still think that a Huguenot Florida would remain loyal - further so because it would be a natural destination for Loyalist refugees from the south. As for the greater geopolitics, I already made clear my opinion on the excellent opportunity for the British to barr the American westwards expansion. Such a move would have major long-term consequences, as I had already said, seriously affecting the geopolitics of Europe and the world.
For one thing, the Monroe Doctrine entirely rested on Anglo-American cooperation, impossible on those conditions. While Britain and America are deadlocked in the various border clashes and frontier wars, the Spanish will probably get another chance to retake their Latin American holdings, with French assistance. I doubt that they would be very succesful, but still, some regions might be retaken.
I don't think it would be enough to prevent the July Revolution, or 1848 for that matter (but there ofcourse will be some changes); when Napoleon III comes to power however, we will get a major change. France, Spain and USA in this world will be natural allies; together with various rebels and Latin American countries they will challenge the British naval supremacy and domination in the Carribean; and that will ofcourse mean no Anglo-French Entente. Very possibly Russians will not have to fight a Crimean War, but instead will impose various concessions from the Ottoman Empire; it is however also possible that Austria, Prussia or both might ally with Turkey, at British instigation.
World War One in the 1850s is a possibility.
