Let's take some examples of some "flagship" western European countries, such as Germany or the UK. These 2 countries have constantly classified the risk level of other countries, forbidding/warning their citizen to not travel abroad in "risk areas", despite themselves having, at times, much higher infection rates than any other country they classified at risk. It was specifically the case in the first half of 2021.
A counter example, the US is as big as the whole of Europe and they didn't "compartimentize" their states like it happened in Europe. And they just did ok (compared to Europe)
One has to realize that Europe is a patchwork of countries which have always fought against each other since history remembers, and "Schengen rules" is a new thing which is not deeply changing the culture and instincts of these countries and their citizen.
People had antibodies in the states in December 19 according to the CDC. This also matches some anecdotal accounts from a girl on instagram that claimed her family had COVID in 2019 in the States after a visit from China.
We probably didn't notice because COVID mortality is pretty low.
Containing such an easily transmissible virus is also pretty much close impossible, no amount of lockdown would have killed it.
