As of September 11, 2018, the current administration's draconian new visa rules go into effect, making life a lot harder for foreign artists wishing to work in the US, and American agents and opera companies who are hoping to bring them here.
Never fear --- Brian Taylor Goldstein, Esq., Robyn Guilliams, Esq., and Christopher Dowley, Esq. are here to help you unravel this morass via their article on the Musical America Blogs, entitled, THE ARTIST VISA UPDATE FROM HELL.
It's fairly named.