Even if everything was in stock I'd expect my overall online purchases to decline in the next few months. I'm not really worried about new clothes if I'm not going outside, and a lot of things like toys and gadgets I usually waste money on seem a lot less important with a worldwide pandemic growing exponentially outside. I'm probably an outlier though in terms of how much I spend/waste on online shopping discretionary spending in normal circumstances (and a lot of that discretionary spending like clothes is not going to amazon anyway).
Do you have any idea what the full industrial capacity of the American economy is? These type of basic items are all dead-simple to manufacture, and highly unlikely to run into supply-chain interruptions.
I guarantee you that once Americans get the full on prepping instinct out of their system, the inventories will all be replenished by next week at the latest. This isn't the collapse of industrial civilization. The factories are churning at 100% capacity.
People won't keep stockpiling six months of toilet paper every single week. There's virtually zero chance that there's any significant supply interruption beyond a few days.
We are a few weeks ahead of you here in Australia on the panic buying and toilet paper is one of the few things we actually produce here.
But it's still impossible to get in most places a few weeks after the panic buying first happened. People seem to buy it immediately on reflex, and people who didn't panic buy are beginning to panic search for it.
One factor is that toilet paper is a bulky item, which makes the logistics of shipping and storage tricky. But still! I'm very surprised at how fragile this (fairly simple) supply chain has proven.