1999 Ford Escort Catalytic converter

Yes, it would cause a loss of power, this loss could be significant depending on how large the restriction is.

To find out, have a backpressure test performed on the CAT.
The O2 sensor is removed and a pressure gauge is screwed in. This will give you definitive evidence that the convertor is clogged.

If convertor is bolted on, remove it and inspect visually. Look for melted material or chunks of material inside.

Clogged convertors are generally caused by am incorrect air/fuel ratio, or an impact (running over a curb), for example.