I Am trying to redo my threshold due to the fact that my floor has been raised like 2". I cannot find any screws and I have been working on it with a crow bar. I have been looking on line and the consensus is that the threshold is typically screwed down. IS it being held in by the door casing. I am going to have to cut it anyway but I wasn't sure how this strip is being held down.
That threshold is part of the entire door system. It wasn't added after the door was installed. It's screwed upward into the jamb sides and may have extrusion fins that engage slots in the jamb. Ordinarily a threshold doesn't wear out before the door system does, so it's rare that a person would try and remove it without replacing the door.
You'll need to figure out how to cut those screws so you don't tear out chunks of jamb. It's made from soft pine and would splinter fairly easily.
Riffing on Isherwood, I would take a hacksaw blade and wrap the end you'll hold in duct tape. If the floor is vinyl or wood, put tape down on floor as well. Slip the hacksaw blade under the threshold, moving it along until you hit a screw. Begin sawing until you've cut through. Repeat process for the other two screws. Once detached from screws, you should be able to wiggle it out using a flat blade screwdriver on the opposite edge.
Edit: It was pointed out to me this method won't work with this threshold, but as Trevor points out in his response, "...use reciprocating saw..." I think that might be it.