is totalitarianism a perversion of nationalism?

Most often it is.
Other times, it is a perversion of internationalism (as for "internationalism of the proletariat").

I'm not sure there's a causal connection, but they do seem to correlate. Totalitarianism, if memory serves, means rule by an undemocratic leadership with dissent not allowed. Nationalism may be used as an excuse to justify such a government.

So, hmmm, maybe yeah, one is a perversion of the other. Interesting question!

One can see that most of past and actual totalitarist regimes have only two causes : cult of personality and greed. Nationalism is almost everytime an excuse to justify them. (I believe).

A totalitarist with success must be the person who has utilized Nationalism well.

(Like Hitler)

Stalin and Mao were totalitarian and they had their own cult of personality even though they're not of nationalist parties. I think that totalitarianism is due to a sociopathic narcissist taking power and often using nationalism to gain the support of people and to brainwash people.

It's interesting though that totalitarianism crumbles in the end. Fascism and Nazism were crushed, there was a period of destalinization in the soviet, and Mao's ideas were not lived up to.