I have been trying (mostly unsuccessfully) to find some decent video of the test boats being built for 2021 America’s cup. Some teams are building slightly smaller test boats to get the technology down, before they build boats for the Louis Vuitton Regatta. The winner of that series will face the defending champions, Emirates Team New Zealand, in Auckland.
This video from the American team from the New York Yacht Club, American Magic is the best I can find. It’s from late last year. There are some good shots of the boat, which is a foiling monohull, flying. Those are right near the end of the video (at 2:20 or so) if you want to skip ahead.
But the best America’s Cup video is still this compilation from the 2013 racing season. It is of the AC72, the giant foiling catamarans that started the whole foiling thing with the America’s Cup. They were 72 feet at the waterline, 86 feet long overall, with a beam (width) of 50 feet. They were ridiculously expensive, and proved very difficult to sail. They were replaced 4 years later by the AC50, which had better tech, and were noticeably cheaper to build.