It is just like if you have assets at a US Bank - although purportedly not at a Swiss bank.
If by "assets" you mean cash on deposit, the FDIC insures those deposits up to a certain amount in case of a bank failure. Coinbase isn't a bank, and their customers' coins aren't insured (unless Coinbase does it by some other means).
Their stock is at all times low
First of all, they've only been a public company for just over a year, and their stock started dropping almost immediately after it was issued--no doubt because investors thought there was going to be much more demand for it than there turned out to be. I just took a look at the stats on my brokerage account, and their P/E is 6.47 right now. That's well below the general market, but for a financial institution that's about what you'd expect. Plus if their earnings keep dropping, that ratio is probably going to increase--and that's what I'm assuming investors are expecting.
Other than that, warning of risks in SEC filings is par for the course for any company. Just look at the annual reports of any company you can think of that's publicly traded. They list off all the risk factors that might put them out of business, no matter how unlikely.