That's the main chain only; Lightning Network and side chains have no such limitations. There are over 36,000 lightning channels that can clear bitcoin transactions without using the main blockchain.
In a shopping mall scenario, most people would already have open channels with their favorite stores, similar to how store credit cards work today.
A cryptocurrency of some sort may eventually become a threat to the US dollar but bitcoin is clearly not it.
If it's going to happen, bitcoin will most certainly be it. The dollar is starting to lose its place as the world's reserve currency; Russia, China, Iran and other countries are cutting side deals to use currencies other than the dollar when they can [1].
Sure, smart people will continue to buy their morning coffee with dollars but they won't be saving for a rainy day in dollars.
The Fed has already printed trillions and trillions of dollars, with no end in sight; it's just a matter of time before we have either negative interest rates or noticeable inflation or both. Regardless, it's losing its buying power daily.
That's why a company like MicroStrategy borrowed $550 million at 0.75% to buy more bitcoin—and that's after a $425 million purchase a couple of months ago. Mass Mutual—an insurance company—just bought $100 million in bitcoin [2].
These and other companies wouldn't have done this if they were confident that the dollar would retain its value.
It looks like the beginning of a speculative attack, which was predicted 6.5 years ago [3].
[1] https://www.lynalden.com/fraying-petrodollar-system/
[2] https://www.kevinrooke.com/post/microstrategys-bitcoin-debt-...
[3] https://nakamotoinstitute.org/mempool/speculative-attack/
