No country can be trusted especially further you are sociopolitically, socioeconomically, historically etc (World is a big thing)....it is all relative and relationships wax and wane as they do due to circumstances of time and space. i.e I remember very well how you described Turk-Azeri relationship as brotherhood (though Azeris have to manage things with Russia and Iran given reality) and maybe India enjoys such a thing with Nepal given deep bonds (that nationstate is nominal thing over it, i.e there is complete freedom of movement between citizens of both countries, and Nepal has reality of China that it has to manage things as well with similarly to your context).
i.e we can make (warm) exceptions to the norm, but the norm is the overall default past these things in the world that is colder to context and "doesn't get you" deep enough like cultural brother. Turkiye is just sufficiently different country in end to "European NATO" (old western or new member eastern components) and "North American NATO" (which has US which is a superpower engaging in Asia, which is where India comes in w.r.t China etc). In fact I would put Turkiye in its completely different category as "Turkiye NATO" or Anatolian NATO etc. European + North American NATO perceives Anatolian NATO as one foot in, one foot out compared to them....whatever the underlying processes of erosion that have occured in last 30 - 40 years to change it from cold war one.
Way I see it is Turkiye's relationship with US is on glide path downwards after cold war ended, the circumstances changed (PKK et al, Iraq war, Israel, Arab world, ISIS, Syria civil war as to how US engaged in these with the bad rating score you know best and can assign regd Turkish own interests - maybe the Iran vector is the only underlying one there is deeper intersection above a 5/10 etc these days).
Whereas US relationship with India is increasingly China-focused (totally different country and context to Russia w.r.t European NATO)
i.e It is kind of opposite of upwards improvement India-US slowly and cautiously have taken (compared to how it was in cold war)....i.e our interests with US align near 10/10 w.r.t PRC.
NATO in Europe was aligned collectively against USSR and Russia fills this role now (for much of US and Europe) after the "Yeltsin and early-Putin detente" phase of 90s and 00's is over and Putin's Russia unhappy with Ukraine's politics and what he saw as encroachment (into crimea given Russian naval base there, and political treatment of Russians in Donbass etc)
In any case US-India one regd anything to do with F-35 (given S-400 specifically) is fraught with fine print details. How to integrate it cohesively (that needs US cooperation + cost to do) given S-400 is baked in and F-35s will be operating in S-400 airspace (and rest of Indian-origin SAM + BMD network), there is all kind of problems even from purely technical standpoint.
i.e the underlying reason the aero india participants of top tier stuff here from adversial entities (Su-57 and F-35) would have most of their radar modes switched off, fresnel lens on etc....and the whole airshow is well away from where S-400s and other heavy Indian AD networks are situated (in north).
Su-57 with Russia would likely be quicker to integrate (given Russian relationship with India since USSR times)...but problem is their production capacity given war with Ukraine (and post war situation they need to divert everything for to flex/deter/maintain).
US has good production capacity in comparison to deliver (a number of squadrons till India can bring AMCA online), but the problem is this integration + political, security aspect of how much US would again trust India to fully air gap S-400 from Russia's radar technicians etc....and then the utility of all of this for India's own RnD and knowhow to use in next chunk of decades too (i.e dependent on how much of a threat China is to India compared to US/West in end...which is simply a very heavy differential now)....and again how US perceives and adjudges that....and puts some premium or fine print carveouts for it.
