From what I’ve read the expectation is that by late May-early June the US will open up vaccination for the general public and any adult who wants one should be able to get one.
I still think Summer’21 is still bushes status, however.
I think in terms of vaccination speed so far things have been moving quickly because the prioritized population is low hanging fruit.
When you move to getting the general adult population vaccinated (or the 75-80% needed for herd immunity) that’s when you’ll see some more road blocks. Just another case of the Pareto Principle/80:20 rule. The country will probably get like 50-60% of the population vaccinated with little hitches. It’s gonna be that last 15-30% that’s gonna prove difficult.
Also, masks are here to stay.