The Miami international airport is the most important in Florida and the surrounding region. Miami is, therefore, the only city in the state which boasts direct flights to many European cities.
If your final destination is Orlando, it's normal to stop over in another city, be it Miami, New York, or Philadelphia. Or another option is flying to Miami, and then heading to Orlando by car, which can end up more comfortable and cheaper.
From Europe, there are any number of airlines to choose from, and if you book at the right time, some great offers to be found.
From the USA
Although Amtrak offers trains from New York to Miami, this option, although perhaps quaint and nostalgic, is too slow and expensive for the majority of travellers. Other East Coast cities such as New York, or Washington are well over a thousand miles away.
If you're planning to visit Orlando, an alternative to landing in Miami to fly directly, as while the city is poorly connected to Europe, it's very well connected to other cities in the USA.
Without too much trouble, it's possible to find flights to Orlando or to Miami from New York for only $80 each way. And if you're in Los Angeles or San Francisco, getting to the USA would cost you approximately $130.
You can look for cheap flights clicking on the link below:
If in the end you decide to fly to Orlando, Key West, or other nearby spots, once you're there the only option is to rent a car. It's best not to rely on public transport in the USA.