For years if someone imagined a WW3 scenario it would start like this:
-Russia steamrolls Poland
-Germany puts up a fight but is overrun
-Then in the battle of Paris, US troops arrive and help European forces stem the Russian onslaught.
But now we've seen the Russian military in action and that the cogs of its' war machine have been thoroughly gonked up by corruption and poor leadership. Now you may think that these issues could be quickly fixed but the deficiencies in Soviet/Russian (vs. NATO) doctrine were illustrated back in the 1991 Gulf War so I doubt resolving these issues would be a "quick fix". And given the performance of the Russian military in Ukraine, I would say that Poland with its' more modernized and organized military than that of Ukraine could mop the floor with them.
So I doubt that the US has to be part of a security architecture to keep it safe. In fact I think had the US not have had such a strong presence in Easter Europe, this war would not have happened. And before you ask, I do believe that Putin wanted to invade Ukraine regardless of what NATO was doing because the fighting is still ongoing even though Zelensky said he wouldn't pursue NATO membership 2+ months ago. However, I don't think he could have gotten enough popular support for the war had it not been for NATO expansion. So it's like asking would the 2003 invasion of Iraq have happened without 9/11.