I seem to recall reading about a mountain in the Atlantic that if the side of it collapsed into the sea would yield a tsunami 500-1000 feet high along the northeast coast of the US.
Yes - Another often-referenced “threat of doom and calamity” - One of the Azores Island mountain slides. It faces the US east coast. If it trips, yes the damage will be horrible. But it a once-in-150,000 year occurrence. If it repeats again at all.