Beside cherry-picking preferred polls, committed Democrats and Republicans will spin narratives of victory to take us to next Tuesday's second presidential encounter. Democrats will emphasize Ryan's muddled counter to the plan to withdraw from Afghanistan in 2014, and will play up the "threat" of his comments on Medicare and Social Security. Republicans will point to the lack of concrete programs put forward by Biden, especially on the economy, as he preferred to challenge Ryan over the GOP plans instead of pushing his own.

All well and good for the base, but it does not really give us any clarity on the key electoral outcome: did either man grab some of the vital votes from America's "independent" center, those who are undecided or swinging back and forth between the two camps? This was not resolved last night, especially with the next two Obama-Romney debates certain to be more influential in determining which campaign can persuade voters to commit.

And so to another outcome which may just as important for us in Britain: for all the verbal combat, the encounter illuminated that the differences between an Obama Administration and a Romney alternative are not as great as advertised.

That was particularly evident on foreign policy, where the concern for many is that a Romney presidency will lead to another misguided overseas adventure. I doubt that concern was eased last night, but at the same time, the debate was notable for how Ryan and Biden effectively converged on a "get tough" posture.

Like Mitt Romney in his heralded speech in Virginia on Monday, Ryan skipped over most of the world. There was nothing on China or Russia, let alone the vanished continents of South America and Africa, and --- compare this to past campaigns --- nothing on Europe and NATO. The international economy, arguably the most important issue right now, did not make even a cameo appearance. Instead, this was a conversation about who could be the harder man over the Middle East and Iran.

That is why Ryan immediately went for the symbol of the attack on the U.S. consulate in Libya, with the supposed administration failure in intelligence and misinformation over a "terrorist" attack. And it is why Biden responded --- with a line which I think shows the limits of the GOP attack --- "we will find and bring to justice the men who did this", before segueing into the claim, "We killed bin Laden; Governor Romney said he wouldn't move heaven and earth to get him." The interpretation was that either an Obama or Romney Administration will pursue that get-tough shift in U.S. foreign policy, pulling back from the on-the-ground commitment in Afghanistan to pursue attacks from the air and through advisors and covert operatives, working with local forces, against bad guys from Yemen to Pakistan to Libya to Somalia.

A similar "tough guy" dance was played out over Iran, identified by moderator Martha Raddatz as the "biggest security issue". Ryan criticized the supposed weakness of the Obama Administration towards the "mullahs". Biden asserted, "These are the most crippling sanctions in history" and then put Ryan into a corner: "You’re going to go to war? Is that what you want to do?" The reality, as the vice president knew, is that the Romney campaign has no further policy, beyond the current economic and covert warfare against the Iranian nuclear program, unless it openly supports an Israeli airstrike.

That is where the debate reached its most dangerous point, given the concerns of America's allies after the experience of the Iraq War in 2003. The Iran exchange was based on Ryan's premise that Tehran is on the verge of "not one but five" bombs: "What we have to do, is change their mind so they stop pursuing nuclear weapons, [but] they’re going faster."

This falsehood --- there is no proof that Iran is pursuing nuclear capability for its military, let alone close to achieving it --- feeds the current talk of "red lines", i.e. when Israel will have clearance to attack. Biden's moment of clarity, "[The Iranians] are a good way away" from any nuclear device, was swept aside by Raddatz's follow-up: "If the Romney-Ryan ticket is elected, can you solve this in two months before spring and avoid nuclear --- nuclear...?" Thus the convergence in that debate --- for an Obama Administration which does not want to endorse military action and for a Romney campaign that might want to do so but not in public --- that there might be no option other than to accept war next year.

On the economic front, the policy discussion was more substantial in highlighting differences between the two men, especially over health care and Social Security. Doing so, however, the debate --- perhaps inadvertently --- pointed to the limits of either campaign putting into place a significant change of policy in 2013. Biden offered nothing beyond general assurances that the administration, as well as coping with the financial crisis of the last four years, would protect the elderly and the sick and reduce unemployment. Ryan's defence of individual initiatives, from tax cuts to Medicare vouchers to sustained defence spending, left the gaping overall question: how can a President Romney reduce taxes, keep the current level of Pentagon funding, and address the federal deficit without a reduction in social spending that would decimate rather than "fix" programs?

Because of that gap, and the general principle of “economics is hard", U.S. coverage of the debate seemed to focus on appearances: "feisty" Biden v. "formidable" Ryan, the vice president's call of "malarkey" v. his would-be successor's composure.

That will be enough to keep the polls close and the chatter loud until next Tuesday, when I suspect the theme in the U.S. will again be style over substance, with the onus on Barack ObamaBarack Hussein ObamaTime for sunshine on Trump-Russia investigation Getting politics out of the pit To cure Congress, elect more former military members MORE to rebound after last week's "loss". However, here in Britain, the question "Where's the difference?" --- as well as the concern surrounding it --- may continue to linger.

Lucas is professor of American Studies at the University of Birmingham and founder/editor of the news site EA WorldView.