Well, to pull up some things that I've groused about on the Threadiverse recently:

In the US, I'd probably support more federal education subsidy, though I'd be also fine with individuals paying more for it. What I would like to see is states paying less, as if people move from state to state, the state that loses population is paying the bill to educate the labor force of the state gaining population, though, so I don't know if that'd meet your concern for "cutting taxes". I'd be okay with paying more to iron out a misincentive, though.

I've wanted the government to deal with looking into existential AI threats. I don't think that it makes sense for private industry to do so -- the incentives there just don't make sense. That'd take funds.

The same would go for certain other technologies that have potential to create existential risks. I don't know what the situation is for genetic engineering, but I expect that there will come a point in time that we are capable-enough at genetic engineering that we can create some pretty unpleasant self-replicating things.

We don't have self-replicating nano-machines either, but those would be something of an analogous risk; this is the gray goo scenario.

https://en.wikipedia.org/wiki/Gray_goo

Gray goo (also spelled as grey goo) is a hypothetical global catastrophic scenario involving molecular nanotechnology in which out-of-control self-replicating machines consume all biomass (and perhaps also everything else) on Earth while building many more of themselves,[1][2] a scenario that has been called ecophagy (the literal consumption of the ecosystem).[3] The original idea assumed machines were designed to have this capability, while popularizations have assumed that machines might somehow gain this capability by accident.

All three of those deal with technologies where one can create systems that rapidly expand without control and which I'd expect to become increasingly-accessible to humanity.

Military: I don't think that we have an effective counter for small UAVs today. This one we're already looking into. The closest thing we have in Ukraine today is maybe VAMPIRE (a vehicle-mounted system that launches APKWS missiles at aircraft). That's relatively cheap as anti-aircraft systems go, but it's still much more costly even in just per-shot variable cost low-end drones. China has enormous production capacity of low-end UAVs.

There are some policies that I think that it's probably most-appropriate for government to tackle, and I'm sure that dealing with them would cost something, but I'm not sure that the main barrier here is the money.

I'm not really a big fan of having radio devices broadcasting unique IDs from a tracking standpoint; a number of widely-used protocols do this. Tire pressure sensors are mandated by government do this. I think that it would be hard to avoid this without government involvement. Industry has little incentive to avoid this.

I think that we still have glaring problems with computer security as things stand; it's an area where I don't think that we are where we'd like to be in 2024, given how connected the world is. I don't have a specific program that could be funded that would fix the problems. In the past, there's been government-funded research here. It has maybe mitigated some problems; I think that Windows having a SAK was probably the result of government requirements.

I've complained about a lack of financial literacy education being made available in public schools. That'd cost something. But I don't know if that could really be a "spend more" thing, since unless one is going to extend time spent in school, it'd involve cutting something else.

I don't have any concrete pet projects, but I've generally not objected to funding basic research on outer space. Cosmology doesn't really have much of a route to a direct return; it's not really something for private industry. But I think that there's value to humanity building its understanding of the universe. NASA's had a list of projects that it had to cut to cover expanding James Webb Space Telescope costs; that may have been a reasonable prioritization, but I kind of regret that we had to give those up, even if they don't directly buy me much other than some novel science stories.

Work towards colonizing outer space is also something that I don't think has a whole lot of near-term potential for commercial return, but I'd like to see it happen -- probably nowhere near within my lifetime -- as maybe one of the better routes to help provide a backup for humanity. It might provide great benefits, but the window for that is just too long for private industry to deal with. It is probably a project that will span a number of generations, but some generation needs to start if it is to happen.

Hmm. I mean, for something to be the remit of government, I'd say that it generally should deal with internalizing an externality or being something that private industry just can't handle, and that's usually due to scale. I'm sure that there are some other things that'd fall under that category. Looking at the above:

• National defense should be done by government, because it deals with internalizing an externality; national defense is a public good.

• Changing who pays for education away from state level deals with internalizing an externality.

• Privacy in radio systems, at least insofar as it applies to systems where network effect applies -- like, say, the Bluetooth network -- involves internalizing an externality; my decision to purchase a device that increases lock-in to a network that limits someone else's privacy has a negative externality for them.

• Computer security has something of a positive externality in that compromise of one device can lead to an attack vector to another. It also runs into a problem where a device is difficult for an end-user to assess the security of; that's not an externality, but having informed consumers is a requirement for an efficient market. I don't know if it's really possible for most consumers to ever reasonably be sufficiently-informed to assess the security of computing devices that they buy across-the-board. It's like asking someone to assess the safety of an aircraft before riding it (where we solved the problem differently, without government spending, by assigning strict liability to manufacturers...maybe we could do that for computers, but that'd kinda kill open source, and I don't much like that idea).

• Financial literacy education...hmm. I guess I could also live with that being in private schools or homeschooling or whatever. It doesn't have to be public schools. But since most people in the US attend a public school, improving the situation there pretty much requires government action.

• Basic research on some things like outer space...I guess I'd say that that provides some benefit. It's non-rivalrous and non-excludable, so it's a public good with positive externalities.

• Colonizing outer space is just outside the kind of time window, I think, that private industry can handle today.