As Simon said, it's a big and rather vague topic.
To improve the US economically, it's important for companies and the US government to realize that long-term research is important. That's how technology advances and improves our lives. That means ways need to be found to fund long-term, blue-sky, what-if research. How? Beats me. But it needs to be done. It took decades of research in solid-state physics and materials to produce the microprocessor. Ground-breaking products like that aren't going to be created by companies that are basing their research funding on their next quarter's stock results.
I think in many ways we're entering the last stages of an incredible boom in the US. As Ben pointed out, after the devastation of WWII, the US was a huge fraction of the world economy. It was easy for one person to work and support a family. Days before then, and these days, it was common for everyone in the family to work - sometimes in multiple jobs. It's disruptive and in many ways unfortunate that those days haven't been continuing, but I don't know if it's possible for them to. The world is growing, and that's a good thing. But it means that our relative advantage is shrinking so we have to work harder to get the same delta in our standard of living.
To improve the fairness and efficiency of the US tax code, ways need to be found to balance the need to fund the important functions of government with the means to pay for it. That means things like finding ways to tax internet commerce fairly. That probably means some sort of national sales tax. And a fair inheretance tax. Means-tested Social Security, Medicare, and even the mortgage-interest deduction. People who are committed to each other as a family should be regarded as such by the legal and tax system. That means, e.g. a 75 year old widower who shares his house with his widowed 78 year old sister should be regarded the same as newlyweds as far as the tax code is concerned. Whether they're married or not shouldn't matter - it's whether they act as a family (and I think a single person can act as a family in this sense - having a home, working, taking care of themselves, etc., etc.). As the Economist argued a few weeks ago, the fixed retirement age should be abandoned. Retirement benefits should be based on age of retirement and life expectancy - not reaching some particular magic age.
Immigration is important. But some way must be found to balance the good features of immigration with its disruptions - e.g. the disruptions that H1B visas can cause. We should straighten out our illegal immigration policies so that we don't have to have periodic amnesties for the millions of economic migrants who are here illegally for years (who also perform important functions in our economy). If we need these people, then we should find a way to make it legal for them to be here.
Taxes on oil and refined products should be increased substantially over time. The money should be used to improve public transportation, fund research on more efficient transportation technologies, fund passenger trains for commuters and long-haul traffic, and improve roads. Oil and gas are too cheap in the US and it causes problems for the country (as Brandioch likes to point out).
The public airwaves should be better-used in the public interest. As a condition of renewal of licences, radio and over-the-air TV should do much more to provide information to people on what their government is doing and where candidates stand. This will help reduce the pressure on them to raise money for campaigns. Cellular radio should be encoraged - to build neighborhoods and to give the national radio chains competition.
I don't like the idea of publically funded campaigns for public office. Who decides who gets funded? The devil's in the details and the incumbents get to write all the details. But our present system is broken - there are too many rules and too many ways around them. More disclosure is needed in ads and in fund-raising.
Microsoft should be broken up. :-) How? I don't know.
No further extensions of the terms of copyright should be permitted. Fair-use terms in the copyright law should be better balanced with the interests of the copyright holder. The conglomerates that control "content" these days are too often abusing their power.
Software "licenses" that give a client none of the rights of a purchaser when they plop down their money should be declared illegal. Software publishers should be forced to balance their rights with those of their customers. Software patents should be carefully re-evaluated. The terms of software copyrights should probably be re-evaluated as well.
Some form of national service should be strongly recommended to everyone between the ages of 18 and 25. The government should encourage it by more than words and some minor tax benefit. I don't at this time think it should be mandatory. I don't see the benefits of reinstating the draft, but I do see benefits in strongly encouraging local and national service in young people.
Property and violent crimes should be treated differently than crimes against society's good-conduct code. People shouldn't go to jail for taking illegal substances (but should be subject to jail if they do violent or dangerous things while taking them). People shouldn't go to jail for reading things that others don't like. Incitement to violence should be strongly discouraged in all aspects of society and severly punished.
Oh, and people should be nice to each other.
That's about it at the moment. :-)
Cheers,
Scott.