How do you explain the story of Prophet Solomon with the people of Sheba, considering that every messenger or prophet was sent specifically to his people, while our Prophet was sent to all of mankind?

The message of Muhammad, peace and blessings be upon him, is universal for all his Ummah until the Day of Judgment. His particularity with the universal message means the survival of his Sharia and that no other messenger will be sent during his time. This is unlike previous messengers, during whose time or after whom another prophet could be sent, abrogating some of their Sharia. Therefore, the call of Solomon, peace be upon him, to the people of Sheba does not diminish the particularity of Prophet Muhammad, peace and blessings be upon him, because Solomon's message did not encompass subsequent generations, nor did his Sharia remain an un-abrogated, firm law until the Day of Judgment, like the Sharia of Prophet Muhammad, peace and blessings be upon him.