Jim Armitage: Fracking future could see Uncle Sam hanging up his policeman's helmet

Global Outlook: It’s not beyond the realms of reason to see China muscling in on the scene to prop up the sheikhs

The US may not feel the need for so many aircraft carriers if it becomes self-sufficient in energy (ALAMY)

By the looks of it, David Cameron won't be legalising drugs anytime soon. So I've been looking for other ways of blowing one's mind. Surprisingly enough, it emerges in a far duller-seeming area of government policy this week: fracking.

Mention the science of extracting hard-to-get gas at tonight's Christmas drinks party and you'll probably soon find yourself alone in the kitchen.

But look deeper into the way it could change the world's economic and political balance and it becomes quite fascinating.

Unfortunately for Britain, even if fracking extracts the most optimistic levels of gas, we're still pretty much doomed to have to continue importing about three-quarters of the stuff that we need in the long term. North Sea supplies are running out and we've opted for a policy of building new, gas-fired power stations over dirtier coal ones to meet our Kyoto targets.

But if the US energy firms keep up their fracking success at these rates, combined with huge gains being made by the likes of BP in its offshore oil industry (glossing over the Macondo disaster for a moment), the world's richest nation should by 2030 or 2040 be entirely energy self-sufficient.

The implications are enormous – nowhere more so than in the Middle East. Just how keen will US popular opinion be during the next recession to continue being the Gulf's policeman? Why does Joe Blow in Ohio care a hoot if the Straits of Hormuz are open or closed if the gasoline in his car is from the good ol' US of A?

Will American taxpayers really want to continue spending countless billions of dollars a year retaining the 40 ships, 175 aircraft and 21,000 military personnel of the US Navy's fabled Sixth Fleet in the Mediterranean if it has no need to keep propping up oil-rich governments in the region?

And if the US is not supporting the House of Saud and all those other dynasties, who will?

Would there be an Arab Spring across the Middle East to kick out the royal families we and the Americans have been supporting since the Second World War? Bahrain came close last year.

A full-scale retrenchment from the region would be unlikely, of course – the Israeli lobby in Washington would make sure of that, but the US presence in much of the region could very much shrunk.

If the US did decide to scale back, it's not beyond the realms of reason to imagine China muscling in on the scene to prop up the sheikhs with a bit of military muscle. After all, China is a massive importer of oil from the region and, as its dealings with mineral-rich countries in Africa show, it prefers to deal with incumbent regimes – no matter how unpleasant they may be – rather than encourage popular uprisings.

As I chatted to a couple of political and oil business sources around this subject, I raised the idea that America may want to keep its grip on the Middle East in order to help out its European allies – primarily us.

Cue polite sniggers. After that had subsided, one suggested the US might offer a compromise whereby European Nato partners take up some of the slack. Can Europe afford it, though? And might not France, with its successful switch to nuclear giving it less of an urgent need to secure its gas provisions, say "non" to a bigger contribution?

Perhaps we'd better start building relations quickly with Russia and not get too prissy about this Litvinenko business. If we're sticking with the gas energy policy we've adopted, the coming decades might see a hold-your-nose attitude to the Kremlin becoming more prevalent in Westminster. Talks are already underway between BP and Russia to extend the Nordstream gas pipeline (which takes gas from Russia to the continent) to the White Cliffs of Dover. Expect some interesting diplomacy beyond that judo match Putin watched with Cameron during the Olympics.

And what happens in the Americas when the US becomes a net exporter? The US may never again feel the need to send Rambo types south of the border to destabilise the likes of oil-rich Venezuela. Washington could destroy Hugo Chavez's regime just by exporting the oil price down to levels with which Caracas can't compete.

So far the fracking boom in the US has not had too much of a radical impact on the global energy markets: not long after it was becoming a big deal in the US public debate, the Fukushima nuclear tragedy happened.

Almost overnight, Japan, the world's third-biggest economy with nearly 130 million electricity-guzzling inhabitants, switched from nuclear to gas. Also as a result of Fukushima, the world's fourth-biggest economy Germany is doing the same.

Events like that make predicting the future for energy – and therefore global politics – rather more of an art than a science. Throw in the occasional monster find in an unexpected area and your predictions go badly awry. Israel recently had a big discovery offshore recently, for example.

Meanwhile, given the rule, as spelled out to me by one thinktanker, that shale gas tends to be biggest "when there's bugger all in the way", it could well transpire that the vast, uninhabited tracts of Australia could be an enormous new supplier.

This would add to coal, iron ore and all the other valuable stuff which the Aussies have been shipping out to China to keep itself recession-free in recent years.

Then you get the surprise failures. Given its success in offshore gas (in partnership with Britain's BG Group), who'd have thought Brazil would struggle to extract its oil reserves? Investors who piled into state-owned Petrobras when it struck black gold in 2007 certainly didn't. They're nursing painful losses as political meddling in the oil market has left the country still importing heavily from the US (yes, the US was already exporting some oil even before fracking).

Once you start playing fracking futurology, you can then start getting into the advanced version of the game – What If? Had the US been self-sufficient, would we have had the invasion of Iraq? And how about Afghanistan? Would al Qaeda even exist if the US did not need such a presence in the Middle East to keep its energy supplies?

Fun to consider, isn't it? There you go. Next time you're at a party and a shifty bloke old enough to know better offers you a funny-looking cigarette, strike up a conversation about fracking instead.