Yes but not the main one.
Half of Teesside is in Co Durham. Sunderland is traditionally Co Durham. The Transporter Bridge and Newport Bridge are half in Durham. Counties have come and gone in Boro: North Riding, Teesside, Cleveland, Ceremonial Bla Bla, and will probably keep coming and going. Riverside literally sits on the border.
The whole of Teesside is industrially, commercially, culturally North East suffering al the same problems as Sunderland and the region. Teesside has nothing to do with woolly back North Yorkshire. Google map England if you're not sure what NE is. It's on your local news, you drive through it for all your away games, you know it. They consider Newcastle their regional capital and go there for concerts, shopping, major events etc. Not many would know Sunderland or go there apart from the trips for footy games but it's their nearest city. Get over it.