Brat,
The design engineering, development, technology advances and integration of systems in the F-35 is beyond the financial ability of any single G7 nation but has been made available to a number of allied Air Forces through a massive ‘successful' collaborative effort of various partners and many would judge it a successful program in any number of ways.
You need to come around from the dark side of the moon. The US had all the financial wherewithal to do the total F-35 just as we had to do the total F-22, just as we had to do the total B-2 bomber and just as we will have to do whatever else comes down the pike that is technologically sensitive. The next US Defense spending budget will be over three quarters of a trillion $$$s.
The reason why we search out partners for some programs is mainly to reduce the purchasing price in the long run for the USAF, USN and USMC for that particular program. It's called "Lets Make A Deal!" I know because I helped with some of the F-16 efforts long ago in this respect. The reason we don't search out partners for some programs is because of proprietary technology protections reasons. For the F-35 program putting it into simple words that you wrote,
the establishment of the massive collaborative effort of various partners was to suck you in to buying the aircraft and reduce the price to our military users, don't know if you are English or not but thanks for your contributions if you are. If you don't believe this, watch what happens if Canada backs out and buys FA-18s from Boeing instead, probably a good deal for both of them. But I don't think they will be making partner parts for the F-35 if that's their final decision.