The first joint session of the United States Congress (Senate and House of Representatives) was held on April 6, 1789, to count electoral votes for the 1789 presidential election, which George Washington won.
Since then joint sessions and joint meetings have been held at irregular intervals. Joint sessions are more formal and primarily reserved for the State of the Union addresses by the president, whereas joint meetings are held when the two legislative bodies agree to meet with each other. It is during joint meetings that foreign dignitaries are invited to deliver an address.
In the past, several foreign dignitaries, usually the heads of states or governments, have addressed these sessions, the most recent being the address by Prime Minister Shinzo Abe of Japan on April 29.
Looking at the history of addresses by foreign heads of states or governments, Israel takes the top place with nine addresses followed by Britain and France, each with six addresses. Late British prime minister Winston Churchill and Israeli Prime Minister Benjamin Netanyahu each has delivered three addresses, taking the top place as individuals.
The US is the No1 ally of Japan, yet this was the first time its prime minister was invited to address a joint meeting.
It is reasonable to assume that the invitations extended to a foreign head of state or head of government to address a joint session is heavily influenced by the strength of the relationship between the two countries.