You can't say that Amazon dominates retail to the extent that Youtube dominates internet video, but there have been a few occasions where Google has kept it's dominant Youtube video off of platforms that Google competes against.

Windows Phone, Echo Show, and Fire TV come to mind.

Is Youtube's share of the online video market large enough that this pattern of behavior would trigger antitrust concerns in the US?

How about under the EU's competition law, which kicks in at a much lower threshold? Would Amazon and Youtube both have a large enough market share to get them into legal hot water for anti-competitive behavior in the EU?