Translation:Which countries have you been to?
In English, this question is in the present perfect tense, have + past participle of the verb. Japanese does not have a present perfect tense. The equivalent of asking a person if they have the experience of doing something is
(past tense of the verb) koto ga arimasu ka?
itta koto ga arimasu ka?
Have you been to ~ ?
To better understand it, ~に行ったこと means "the fact that you have been to~"; Once the subject has been to that place, such fact exists, but not existed, at the time the question is asked. So it is in present tense. You would use past tense if the time reference is in the past: 去年アメリカへ行ったことがありました。Last year I had been to America.
I know the Japanese run the "i" in ni and itta together, but to my ear, unless this is written down, "に行った" , you appear to be missing the vital part of the verb. The audio pauses after "ni" sound, then goes on "takoto... ". Is he/she saying this correctly? Don't like my chances of understanding in Japan if that's correct?