It is almost impossible for the Spouse of a US Citizen who is living abroad to visit the U.S.
Of course it's easy for said spouse to IMMIGRATE to America, but if said spouse wishes to just visit, she will be denied on the ground that the embassy believes she has intent to immigrate.
EXAMPLE
If a US citizens spouse applies for a visitors Visa to the U.S., he or she will be denied on the grounds that the embassy believes he or she has intent to immigrate. However, still just wanting to visit, if he or she applies for an immigration visa, they will be denied because they DON'T want to immigrate, because they still want to live in China.
There are countless stories of expats who have to leave their wives abroad while they visit America, due to the embassy denying their visa.