US and UK have very similar vaccination rates despite the US being open to more age ranges. This indicates that a higher percentage of eligible people have gotten the vaccine in the UK, and the US has somewhat hit a wall in terms of vaccinations (though there is the concern that the rates will slow down in the UK also).

I must admit, it has been strange seeing my US peers getting the vaccine months before I can in the UK, but I guess I take comfort knowing that both countries are still doing pretty well!