There are two US units that are developing 6th generation jets. The one by Air forces defense program will be in operation in 2030. This one will replace F-22. and another one by US Navy will be released before and this one will replace F-18 Super Hornet. I think you are wrong to say that US cannot make. USA is just being USA. They perfect their crafts before releasing them. Unlike, China, quality is not the top priority.