There are differences. Having practiced in all three (Vajrayana, Mahayana - zen, Thich Nhat Nah... and Theravada) the experiences were sometimes vastly different. But this was not really for the reasons that used to cause a lot of chaos and debate on places like E-sangha where triumphalist assertions based on really old formulations of superiority were rife.
The extent to which the outward cultural expressions and use of traditional terminology were present in the teaching and general atmosphere of the respective groups seemed to me to have the most effect on differentiating.
There are age-old doctrinal disputes which show up in the language too, like the notorious word "hinayana", which sometimes got projected onto Theravada. Even if they tried to be politically correct by using the term Theravada it was often clearly in place of "hinayana" with the connotations left in tact. However, in large part, I didnt run into circumstances, except online where anyone truly exhibited very problematic triumphalism. Sectarianism, sure, but that was just as often towards other groups within ones own larger tradition as it was towards other so-called yanas.
More often I found something of the opposite. Theravada teachers comfortably using terms normally used with connotations associated with Mahayana like 'emptiness' and 'compassion', quoting Suzuki Roshi or the Dalai Lama or Thich Naht Hanh. Indeed if I recall, Bikkhu Bodhi lives or lived in a Chinese Mahayana center. My first Tibetan teacher was sent by the Dalai Lama to go to Thailand to study and practice Vipassana. I remember once for his dharma talk he read from Kornfield's A Path with Heart and gave commentary. In my Zen community, I was often asked by other students who had only tried zen how Tibetan or Theravadin Buddhism would view thisor that. In fact for a fundraiser for a prison program I was asked to find a qualified Tonglen teacher to give a workshop.
Lastly, there is Thich Nhat Hanh. I have never met anyone, anywhere, from any tradition, teacher or student, who didnt just adore him, let alone fundamentally disagreed with him.
Hope this helps.