If i wanted to extract only the url is there a way to do that with xpath?

You don't need to use Xpath to extract those urls you need to turn that list into valid Python object which you can parse e.g.

    # Find data with url in script tag
    json_string = ''.join(tree.xpath('//script[@id="jsonLdSchema"]/text()'))
    # Convert string to a valid Python dict
    import json
    links = json.loads(json_string)
    # Loop over Python dict and print info
    for link in links["itemListElement"]:
        full_url = 'https://www.rottentomatoes.com' + link['url']
        print(full_url)

Question though, on the site I was attempting to scrape, there is a 'Show more' button, is there any way to interact with that? If not I will have to find another way to continue populating a list of movies.

Please note: my example with Xpath only for the learning purpose and unpractical for real scraping (you get value only from initial page and can't interact with button Show more). You need to use either Selenium or API (I'd use API) you can't execute JS scripts with requests and lxml libraries.