I believe you underestimate the modal American congress-person and rate-payer.

In congress, maybe about 25% of them can't be bothered to remember what state they're from. They don't really matter as they'll pretty much vote however the last person to talk to them wants them to vote. This is why congressional legislative directors try to schedule appointments immediately before their congress-person votes.

About 10% of congress-people are SUPER sharp and will understand this whole "you have to break eggs to make an omelet" concept. 50% more could be educated. The remainder will act randomly depending on what the internal polling says.

SSL and Boeing and the old school guys know a critical part of their job is to lobby congress-persons and staffers. They're not paying them off, they're just making campaign contributions to ensure they get access to pitch their side of the story.

As for the modal American voter? They don't care about space. They care about whether they're getting a raise next year, the mortgage is paid and inflation doesn't price them out of a good meal every now and again. When they get economic security, THEN they start caring about other things like who goes in what bathroom, why they can't buy TANG or light-bulbs at the grocery store anymore or whether they're getting value for money in their national space program.

My gut feeling after doing polling for a few years is the numbers are about the same: 25% of American voters can't tie their shoe-laces, 10% will understand you sometimes fail when you try to do something innovative and the remainder will need some convincing.

The good news is (effectively) no-one in the US looks at national budgets. Heck, most congressional staffers never read the whole thing, just the bits they're interested in. Many (most?) voters (and congress-persons) look to membership organizations for direction. If someone is a member of the Planetary Society, and they happen to be chatting w/ their elected representative, you can be pretty sure they'll mention how important the space program is. If someone is a member of Drunk Middle-Aged Regressive Science Haters of America, you can probably guess what they think about anything with the pong of science about it. Fortunately, this latter class of Americans usually doesn't know who their congress-person is or that they have a congressional representative.

So... to make an already long post short... I don't think you have to convince EVERYBODY, just the people that matter. The message that "it's okay to fail from time to time as long as you're making substantial forward progress" is something at least half of the people who affect US budget priorities can get their brainstems around.

[And as an aside... having worked with US congress-people in the past, I can report they're frequently much smarter than you give them credit for. And you don't get to be a Legislative Director in a congressional staff without being reasonably sharp. But they do worry about how large donors will respond to their votes. We're entering a phase of debt-ceiling debates. The GOP controls congress at the moment and we'll see a lot of wheeling and/or dealing. It's quite telling to see what each party thinks is important. Biden seems to have invested a small portion of personal reputation in the SLS, probably because of it's history over the Obama administration. Despite it's actual benefits, various GOP members may use that to rail against it (SLS) as a proxy for railing against Biden. (I'm trying to avoid being partisan here, some Dems railed against the Constellation program during the Bush years, so I'm not saying it's ONLY something the GOP does. It's just the typical railing against the other party to try and fire up your base so you don't have to explain why you didn't follow-through on your campaign promises.) But I ramble...]