I have a Huffy All American 10-speed road bike and looking for a replacement for the rear derailleur. Any suggestions?
To be honest, that might be salvageable. Slacken the B screw and see if you can pull it down to the normal position. You will have to remove the chain from behind the freewheel anyway. This could be tightly wedged in there.
That mechanism doesn't look original - so this may have happened before?
You'll want to eyeball the hanger, then test it with a straightedge ruler, and then gently bend it back to position if its not straight... and if it snaps, you'll have to obtain a replacement.
Second part is "how did this happen?" then "what can be done to stop it reoccurring?"
Often the rear mech catches a spoke and gets pulled around, but in your case it looks like the chain jumped the big cog and is now wedged between spokes and freewheel.
Stop it happening again by adjusting the big-cog limit screw on the RD mech. You may also choose to fit a spoke protector/dork disk under the freewheel. My old 5 speed had a classy metal one, but most are clear plastic.
Follow-on damage might include where the chain has munched on the curve of the spokes. I had this on a MTB and because I pedalled a bit, the chain had bitten halfway through some spokes. They broke soon afterward, in the next week or so.
Getting the chain out required removing the freewheel/cassette. You might be luckier if its not as tight.