An external hard drive is nothing but a hard drive (same as the one which comes with any system) which has been put inside an enclosure that provides USB connectivity. If users remove the hard drive inside from the enclosure, it can be directly attached to the motherboard.
Seagate is probably about as reputable as a drive maker can be, IMO. The problem is that...anything manmade can fail at any time. Hard drives fall into that vast category. Which is why backing up the system or valuable data files...has been strongly recommended by everyone since PCs became commonplace and popular.
There are programs that offer some hope to users with drive problems...they are known as data recovery programs.
Before we go further...just what steps did you take to verify that the drive is dead? I ask this since the drive itself may be good, but the enclosure may be dead. Since the enclosure contains the drive, how would a user know?
And how large is the stated size of this external drive?