So according to real protocol, if I am Governor Kaine and I reach out and shake her hand for 7 seconds or whatever it is, instead of bowing to her, that’s technically OK by her?
According to American protocol, yes.
The only exception I can think of is with regards to the Japanese, who do not shake hands - and in which case, the American politician or citizen assigned to greet the ambassador or other figure should bow in the degree of equals, or in the degree of the superior.
Also, from what I understand, Elizabeth isn’t exactly a stuck-up Royal; when she was younger, she was a pretty good truck mechanic.