You are correct. Until very recently, there were no vaccines for rabbits in the USA. Myxomatosis and RHDV were not found here. From what I understand, they don’t spread as easily because our wild rabbits are not the same as European wild rabbits. European wild rabbits are the same species as domesticated rabbits.
There have been some outbreaks of Myxomatosis in certain states. From what I have read, these outbreaks are linked to areas where a species of wild rabbit (called brush rabbits) naturally live. For the USA, this seems to be the states of Oregon and California. The strain of myxomatosis is different from the European strain and there is no vaccine available. They recommend people house their rabbits indoors and use monthly flea protection if they live in the affected states.
RHDV has a history of popping up in small, isolated outbreaks here and there. These outbreaks were often associated with rabbit farms and breeding operations. It wasn’t believed that wild cottontails could spread the disease. In April 2020, a RHDV2 outbreak made the leap to wild species and is now spreading across the country. Currently, it is just in the western states, but they suspect it will eventually be coast to coast. The good news is that there IS a vaccine that was just recently approved. It may not be available in states where the disease has not been found yet, but they are working on getting the vaccine out in the states that need it most right now.
So for myxomatosis, you may or may not need to worry… depending on where you move to. As for RHDV, there is a vaccine now.