Interestingly, the video goes into exactly why there are so many quality sleeper train offerings in Europe compared to North America. In North America, most of the tracks are privately-owned freight rail, and the rest is a patchwork of local monopolies of passenger rail (e.g., Amtrak, Via Rail, regional/commuter rail, etc.), and none of them are being made to cooperate or allow interoperability.
Whereas in Europe, having so many countries in such close proximity, they were forced to make their systems interoperable and standardized and allowing open access (much like roads are open access to drivers or buses), so what you get is many state-run operators and private operators in a competitive market without local monopolies. The result is high competitiveness, high standardization, high interoperability, and thus high quality and availability of service for competitive prices.