How to make unique add_filter to the_content of specific page template files – so each template gets its own addition

You can get the name from the global $template. I don’t know of a way to get it with an API call instead of a global, but such is life.

function floridacontent( $content ){
    global $template;
    $name = basename( $template, '.php' );
    if( 'page-florida' == $name ){
        $content .= 'Forida added content';
    }
    return $content;
}
add_filter( 'the_content', 'floridacontent' );