That's not exactly how that works. The light from galaxies and other Deep Sky Objects (DSOs) are too faint for the human eye. Only with much more sensitive electronic chips or the longer accumulation of photons from long exposures do we get to see these DSOs. Also, a lot of these DSOs are hidden out of the visible light spectrum.

So if the earth was to suddenly lose its atmosphere today, we wouldn't be seeing DSOs tonight. However, the stars and stuff we can see would suddenly stop twinkling.

On a night with good conditions I can recognize for instance Andromeda Galaxy, Orion Nebula, and the hazy stuff around the Plejades with my bare eyes, though faint, and not colored like with astrophotography. Are you telling me I couldn't see them better without atmosphere? Do I have owl eyes, or what?

Okay, now you're going to make me qualify it based on the object's magnitude. Let's try this. If the earth lost its atmosphere today, you would not suddenly see things tonight that you wouldn't normally have seen before.*

*If you live some place with so much humidity/heat that the air was always working against to you seeing things clearly that now are suddenly clear, maybe you'll see more. However, other places on the planet still saw them. Kind of like living in a large city with horrible light pollution. Just because you can't see them doesn't mean they're not visible elsewhere.

You know? A long time ago I bicycled far through the forest with a self-built trailer for transporting my 'lil' Newton' in the late evening, especially during winter. Breathing in trough the nose, and exhaling through a few meters of garden hose to avoid condensation. Somewhere near there:

https://en.wikipedia.org/wiki/TIRA

Though that was about 1980, not as light-polluted as it is now. I don't do things like that anymore, but I'm still thinking I'm not talking non-sense when it comes to that stuff (magnitudes, etc.)

Maybe I have owl eyes ;-)