In the basic plan, the JSF international partners are due to buy 730 jets.
100 are already gone due to cutbacks in Italy, Canada, Netherlands &c. (It's actually 104 but I am giving credit for the Noggies, who have upped their order.)
Of the remaining 630, about 300 are at risk. This includes the UK's aircraft beyond the initial 48, Italy being broke, the Netherlands arguing among themselves &c.
Moreover, the plan was for the international partners to buy heavily near the start of production (in the "program of record" they buy most of their jets by 2020). Now that the loyal Noggies have stretched their buy through 2024, others will follow suit.
Some of this is made up for by Japan (42) and the aircraft provided to Israel by the US taxpayer, but not all. Korea may well go F-15SE.
In the US, the USAF is unlikely to afford the planned buy rate but is not being allowed to say so, while the USN CV community is ambivalent at best to JSF, believing that Hornet/Growler upgrades offer a far better return on investment for the next decade. (Consider that manned deep strike, where stealth is most valuable, is not as crucial for the Navy as for the AF, and besides they have Tomahawks for that.)
The death spiral is very much a possibility.