“Can they send National Guard Troops out of their states to Texas?”
Abbott is using the State Guard, not the National Guard.
The State Guard is not part of the army and cannot be Federalized. I am not sure if other States have a militia like this or not. The State Guard is basically a disaster relief and auxiliary law enforcement organization.
Iowa, and I think some other states, sent National Guard and state LEOs to Texas border this past summer.
Bump
Yes, many other States have similar State Guards like Texas. Check out SGAUS. They go by different names, but are under State control only. They cannot be Federalized like State National Guard units can be.