using one of these these adapters
There actually not adapters. If you look, there NEMA 6-15P & 6-50P on both ends which is US standard 240V outlets.
…a 240V appliance will not use an ordinary plug… You need to import a 240V appliance from a different country…
There actually are 240V appliances with a US NEMA 6-15P & 6-50P plug. You’re just not going to find them at wallmart, there usually used by businesses like mom & pop shops. For example, this expensive mf. For imported appliances all you need is an adapter from NEMA 6-15P/6-50P to whatever that particular 240v rated appliance is using.