If poland really wants to guarantee its safety from russian invasion, it should stop insisting on NATO using americans as cannon fodder and get to work on a nuclear program. Really, I've never understood why they didn't begin one as soon as the soviet union collapsed.
The irony of that statement is that both USA and most of NATO would be the ones to lose their marbles if Poland tried to do that.
They havnt had the tech/capabilities, or were not allowed. Trump set forth helping them before he got out
The NPT and diplomatic aspect is the main issue, in addition to actually building the damn reactors, which is kinda being done, its being put off in time, and Germany&co are lobbying against it, and that's just reactors for energy. Half of the EU would throw a fit in Poland just showed a middle finger to the NPT and just started making weapons grade nuclear material of some kind. Then there would also need to be some delivery mechanism with some kind of deterrence value, yet we don't have a ballistic missile program ready, and all the other potentially convertible options are foreign made and hence would be a bitch to convert.
Because nuclear program is expensive and EU&USA would sanction them, ruining their economy.
The sanctions are a far bigger problem. Poland has double the GDP of Pakistan, and over 30x the GDP of North Korea, and somewhat better technological base than both. Contrary to popular belief, nukes aren't that expensive to build (Soviet Union was not exactly rich, but could afford tens of thousands for some time), or technologically challenging for that matter by modern technological standards at least (see: North Korea and Pakistan pulling it off). Maintaining a lot of long range ballistic missiles is what's expensive, while for its purposes of deterring Russia, Poland would barely need 1000-2000km ranged weapons, so MRBMs and cruise missiles.