POTUS can deliver whatever speech he wants from wherever he wants but he can not call a joint session of congress.
pasta
A Joint Meeting takes place when the House and Senate agree to recess and meet with the other chamber. The purpose of a joint meeting has usually been for Congress to hear an address from an important figure—generally a visiting foreign leader. This practice became a standard part of foreign leaders’ state visits to the United States after 1945.
A Joint Session takes place when the House and Senate adopt a concurrent resolution. Joint Sessions typically are reserved to hear an address from the President of the United States or to count presidential electoral votes as specified by the U.S. Constitution (Article I, section 1; 12th Amendment). On January 6, 1941, two Joint Sessions were held the same day: to count the presidential electoral votes and to hear President Franklin Roosevelt deliver his Annual Message to Congress.
The Speaker of the House of Representatives usually presides over Joint Sessions and Joint Meetings; however, the President of the Senate presides over Joint Sessions where the electoral votes are counted, as required by the Constitution (Article I, section 1; 12th Amendment).
Sauce
https://history.house.gov/Institution/Joint-Sessions/Joint-Sessions/