So a human cannot oppose themselves to an angelic being? People oppose God Himself all the time. It doesn't say Michael had to "woop" him, necessarily, as if there was some kind of physical confrontation. I would say no human could resist an angel physically for long at all, the one exception in Scripture being Jacob, whose wrestling with the angel was by Divine appointment and for a purpose not then known to himself (not known to Jacob, that is).
If the prince of Persia was in fact Cyrus, then him withstanding Gabriel would mean the following:
Gabriel was involved in convincing Cyrus to restore Jerusalem, something he would in no wise be naturally disposed to do. So God sent an angel to influence him to accomplish the Divine purpose. But, at a certain point, Cyrus was backing out of it, having second thoughts, being swayed against such a move by his advisors and councilors. So he was "withstanding" Gabriel in that sense. The opposition was of such nature and character that Michael had to assist. When Gabriel was done meeting with Daniel, he was to return to Cyrus in order to continue influencing him to carry out God's plan for the restoration of Jerusalem. This was to be done because the prophesied prince of Greece was coming to conquer Persia, and the restoration of Jerusalem must be started before that happened, and indeed it must be started on a specific timetable in order for the Seventy Weeks prophecy to run its proper course.
Daniel 11:1 Also I in the first year of Darius the Mede, even I, stood to confirm and to strengthen him.
The verses immediately before and after this one show that it is Gabriel speaking. Gabriel explicitly says that he was involved with Darius (a prior ruler of Persia), to "confirm and strengthen him". This shows that the idea of angelic beings influencing human rulers to fulfill the Plans of God is perfectly Biblical.
In addition, since angels are almost always mistaken for humans, it is entirely possible that Gabriel was an angelic being who was also in fact a member of Cyrus' imperial court, serving as an advisor. Michael may also have appeared in such a fashion. This might explain the meaning of the following statement:
Daniel 10:13 But the prince of the kingdom of Persia withstood me one and twenty days: but, lo, Michael, one of the chief princes, came to help me; and I remained there with the kings of Persia.
Gabriel was there "with the kings of Persia", that is, with the various nobles of the Persian court. Doing what? Obviously influencing the court to promote the Divine plan to rebuild Jerusalem.