What if the Fellowship had stayed together?

What if they had cross the Anduin before the Uruk Hai reached Sarn Gebir? In the film Legolas briefly suggests they should cross the river straight away but Aragorn rebukes him saying Orcs patrol the eastern shore. With Boromir, Aragorn and Legolas, Frodo's journey to Mordor would have been safer and speedier, however there would of course have been great reprecusions for the Manish kingdoms of Middle earth. Gandalf would have gone to Edoras alone; without Aragorn, Rohan likely would have been overrun by Isengard. Gondor also, without the aid of Rohan and the dead army would have been overrun by Morder, Harad and Umbar. So there would have been a situation where the ring may have been destroyed, yet much of Middle earth would have been left in ruins, like when the hobbits return to the shire and find it ruined, despite the wider victory