Como dizer "demorou pra responder" em inglês

Uma boa opção para se dizer isso é com "take a long time" (demorar).

Você demorou para responder.
You took a long time to answer/reply.

Bons estudos.

Opção:

"You took too long..."

And there is also the "stalling" (the stalling, delaying especially by refusing to answer questions or cooperate, or evade the question for awhile.)

Shawn "So, why have you been avoiding my phone calls?"
Serenity "Ah, poor baby, I am so sorry you poor ego is easily bruised. I thought a man of your caliber had thougher skin, a more enduring ego...
Shawn "You´re stalling and you still haven´t answered my question.
...She said "Perhaps I don´t want to answer your question...
Shawn came "Fair enough."...

From the Novel Unbreakable Love by Lance J. Kendrick

So, Shawn had said "você está demorando pra/a responder minha pergunta (sugerindo, que ela está dando voltas, evitando dar uma resposta.)

Piggybacking on the one from Marcio:
You too so long to answer...

You took a while to respond..
You took forever to reply..
You took ages to reply..
You ignored me..
You didn't answer me instantaneously...

Good takes! congrats.