First of all, I want to make sure if I understand your question correctly.
Do you mean the situation when you visited many countries, and one of them was Iceland? So, for example, you started from A-land, then traveled to Iceland, and from Iceland you moved to B-land? And you are confused by the fact that A-land and B-land are different locations. Is that what you mean?

If my guess is right: It only depends on what you focus at. Do you want to focus on your visiting Iceland? Regardless of the trip details? Or are you going to describe your whole journey?

Option 1. Someone is telling a story about Iceland. Or maybe you are seeing it in TV news etc. And you want to inform the other people that you have also visited Iceland (at least once in your life). And that's all. I.e., you are not going to specify any details that there were multiple countries you visited etc.

So, "Я был в Исландии. Я ездил в Исландию. Я съездил в Исландию." are all the possible options. "Я был в Исландии" is the most generic one. "Я ездил в Исландию" is also a mere statement of fact that it happened to you once in the past, but unlike "Я был в Исландии", the latter (Я ездил в Исландию) usually assumes you are going to provide some more details about your trip to Iceland. "Я съездил в Исландию" is almost the same, but there is a subtle nuance. This phrase (with perfective past) is appropriate when the other people expected from you to have visited Iceland. E.g., you shared your plans about visiting Iceland before. And now you inform them of the result: "Я съездил в Исландию". If being said without this preliminary context, the use of perfective would sound unusual, nevertheless perfectly understandable.

In some contexts, the both versions (ездил и съездил) are interchangeable. For example, when answering someone's question on how you spent your vacation, you can choose either of them. It can be imperfective (narrative past) or it can be perfective (assuming you completed your plans for vacation successfully).

Returning to option 1: here it does not matter what the whole trip was like (I mean the other countries you visited or not visited). You only focus on your trip to Iceland.

Option 2. You had a nice vacation and you succeeded in visiting multiple countries. Now you want to share your trip details with your friends. There are also multiple possibilities for you:

- Я посетил много стран. Я был в Норвегии, в Исландии, в Канаде.
- Я посетил много стран. Я ездил в Норвегию, в Исландию, в Канаду.
- Я посетил много стран. Я съездил в Норвегию, в Исландию, в Канаду.
(Those verbs are the same as for Option 1).

- Я посетил много стран. Сначала я поехал в Норвегию. Там я провёл три дня. Из Норвегии я поехал (или поплыл) в Исландию на корабле. В Исландии я был целую неделю. Из Исландии я полетел самолётом в Канаду.

I hope you've got the idea Please let me know if it answers your original question.