No, speaking as a former glaciologist, that's not likely to be true. The parent poster is correct. Younger Dryas featured multiple advances and retreats, which is inconsistent with an impact. Multiple impact over many centuries just isn't that statistically likely, and we would see better evidence of it.
Instead, the most probably cause is freshwater pulses coming out of the melting Laurentide ice sheet changing circulation in the Atlantic. This is actually quite well supported.
Younger Dryas was also confined to the parts of the northern hemisphere, mainly in higher latitudes. A large enough impact to significantly alter climate would see the resulting particulates globally mix in the atmosphere, resulting in more uniform cooling.
Instead, the fact that it was confined to parts of the northern hemisphere also supports the freshwater pulse hypothesis, since it is only a change in the transport of heat from the tropics to the pole, not a change in total heat.
The fact that freshwater pulses from the Laurentide ice sheet caused so much cooling is actually a concern with climate change. It's possible that it could happen again with melting of the Greenland Ice Sheet, at least a weakened version of it (the Laurentide Ice Sheet dwarfed the GIS).