It's good practice to verify any footage you use, regardless of source. Lots of people think they own copyright to certain things when they actually don't.
With Archive.org you need to really read the different licensing they use – not all of it is public domain. Some requires attribution, some can be used in a noncommercial way, etc. I've seen media that had no copyright/licensing information provided. So just residing on the site doesn't mean public domain.
Get whatever information provided and if there isn't any, do some more research on it. This can be useful when getting E&O insurance. Also, it's good practice to have an entertainment/copyright attorney look over you stuff. (and do find a lawyer that specializes in this, as not all lawyers have equal knowledge. A good friend of mine is a top notch real estate attorney, and he won't touch copyright – "it's not what I do, so I can't provide solid legal opinions". )