But since you bring it up, the invasion of Denmark in 1940 showcases the exact reason why tiny countries like Denmark and Belgium shouldn't invest in such a limited number of highly valuable and resource demanding assets as F-35s. The entire Air Force (including state-of-the-art Fokker D.XXIs) was based at just one airbase, and was wiped out in a matter of minutes.
The difference is that Danish forces remain part of NATO today and have a much better collective defence agreement, with supporting NATO forces and infrastructure, than was present 78 years ago.
With such a small number of F-35s in such a small country, exactly how long do you think it will take for an enemy to wipe them all out? You are playing a big-boys game with these overpriced toys, but without the size to ever be relevant and all the downsides of being a tiny player.
The problem with that statement is you have a single world ending scenario to justify your claim which ignores membership and the collective defence of NATO. In opposition to that claim of irrelevance are the many times Danish and Belgian F-16s have deployed on NATO operations over the last 30 years.
1999 nine F-16 fighters as part of Operation Allied Force.
2002 and 2003 six F-16 fighter bombers flew 743 sorties during Operation Enduring Freedom.
2004, four F-16 fighters was Denmark's contribution to NATO's Operation Baltic Air Policing. The air policing mission was also undertaken by Danish F-16s in 2009, 2011 and 2013
2011, six F-16 aircraft assisted in maintaining the no-fly zone over Libya as part of the 2011 coalition intervention in Libya.
2014, seven F-16 flew against the Islamic State forces (ISIS / ISIL) as part of Operation Inherent Resolve.
1996 F-16s enforced the no fly zone over Yugoslavia supporting UN and NATO troops
1999, twelve Belgian F-16s carried out 679 combat sorties
2004, four F-16s worked under NATO's Baltic Air Policing and again in 2006 and 2013
2008, four F-16s were deployed to Afghanistan in support of the Dutch land forces
2011, Belgium deployed six F-16 in support of Operation Odyssey Dawn, to support the NATO operations over Libya
2014 six F-16s were deployed under Operation Desert Falcon as part of military intervention against the Islamic State of Iraq and the Levant
Clearly these small Air Forces have been able to positively contribute to NATO operations and the contributions they make are valued politically, hence the continued funding of an Air Force with the capability to fulfil NATO mission requirements.