It looks like you have a 1/2″ sweated copper male-threaded adapter onto which the pot-metal tub spigot (the part you hackswaed out) was screwed. If so, don’t try to use a pipe wrench to twist it apart. You’ll need to heat up the male adapter with a torch to melt the solder and caefully pull the adapter off with Channel-Lock pliers. Then snad down and clean the end of the horizontal copper pipe section, resolder on a new male adapter, and then screw on the replacement spigot.
Looks like there is a lot of corrosion at the end of the pipe, and hopefully its just at the end where the old spigot was attached.
If you are careful, you won’t damage the proximal ends of the connection, but don’t count on it. If you can’t fix it using my suggested technique, you’ll have to get behind the tub somehow. The best way to do that would be to get access to the wall behind the tub.
Good luck,
NtP