If you're married and your H is American, then getting a green card and eventual citizenship will be straightforward.
You will have hoops to jump through to prove you're married, etc. The process takes a lot of time. You would probably initially enter the US with a spouse visa and proceed to the green card application once you get there.
Has your child been registered as an American citizen with foreign birth (dual citizenship with UK)?
There are pros and cons to Florida. From a distance the US can seem very foreign, very scary, very alien. Yet 350+ million people call it home and live ordinary lives there, some comfortable, some less so, just as you would find everywhere else. It's not the UK. It has a different culture. It has a lot to offer all the same, particularly in terms of opportunities for children. Sports are huge in Florida and you can play outdoor sports year round.
If you and your H can do a cost benefit analysis, with a realistic idea of housing costs, taxes, educational opportunities all the way to university (University of Florida is very affordable for residents), extra curricular opportunities, food, utilities, insurance, cars, healthcare/ insurance, etc, you can get an idea of the quality of life you can expect.
Be sure you can get back to the UK every year as much as you want to. That's a cost you need to factor in too.