Are the Diomede Islands part of North America or Asia? I cannot find a credible, clear answer online. Only that the islands were part of the land bridge between the two continents.
From an Earth Sciences perspective there is no distinction between Asia and North America. They are geologically continuous, comprising mostly Mesozoic sediments in a block-faulted continental shelf setting. The Diomede Islands just happen to be the highest points of this tectonically complicated area. That they are islands at all is purely an accident of the current post-glacial sea level rise. The surrounding Bering Strait is only about 50 metres deep, whereas, for most of the last 2 million years the global sea level was up to 120 metres lower than present. Hence it is only recently that the Diomedes became islands at all.