Newly independent states typically struggle to make their way in the world, even in the most favourable conditions. Kosovo's declaration of independence in 2008 was enthusiastically backed by the US, Britain, and many other governments. But six years on, more than one third of UN member states, including five EU countries and four Nato members, continue to withhold recognition. Kosovo has yet to achieve the political stability, physical security and economic prosperity its leaders promised when they broke with Serbia.

An independent Scotland, with its developed economic infrastructure and abundant oil and other natural resources, appears to occupy a more advantageous position than Kosovo or, say, South Sudan (independent since 2011). It is worth noting that South Sudan's oil wealth did not save it from a descent into ethnic conflict and humanitarian crisis last year. But like East Timor (2002) and Bosnia-Herzegovina (1992), South Sudan's independence movement benefited massively from strong international and UN support.

By contrast, Scotland's independence bid has attracted scant international backing. Some of the world's more influential governments, including the US, Canada, India and Australia, are openly opposed.

Others within the EU, notably Spain, are deeply suspicious, given the precedent secession from the UK might set for their own minorities.

As with Kosovo, the silent ambivalence, bordering on hostility, to the SNP-led campaign points to a long and rocky road ahead should the yes camp prevail. All the indications are that full international acceptance of an independent Scotland will be a long time coming. It will certainly take years to achieve, if it is achieved at all, and not occur within the 18-month time-frame envisaged by Alex Salmond.

The Scottish government's white paper, Scotland's Future, identifies EU membership as a central aim, and foresees a "seamless transition" to be completed by March 2016.

But the SNP is already sharply at odds with Brussels over fundamental issues such as currency union, eurozone membership and immigration. And this before the issue of Scotland's putative "share" of the British EU budget rebate is even raised.

Olli Rehn, the EU's former enlargement and economic affairs commissioner, warned again last week that, in the absence of a currency union agreement, an independent Scotland would have to choose between using sterling and joining the EU.

The SNP's claim that Scotland will not have to wait at the back of the queue for EU membership but will automatically join the "top table" has been challenged by other leading officials, including the European commission president, José Manuel Barroso. And it is further undermined by Edinburgh's prospective refusal to join the Schengen agreement on open borders, which all new members are obliged to do.

Even if an independent Scotland did not join Schengen, the prospect of border controls and passport checks between Scotland and England (and Scotland and Northern Ireland) looms large, because Edinburgh's policy on immigration could be markedly different to that of London and Brussels.

Pete Wishart, SNP Westminster home affairs spokesman, suggests, in a recent post on the SNP's website, that, given its "history of depopulation", Scotland would encourage increased overseas immigration – the opposite of what London wants.

The SNP's ambition to immediately join Nato looks similarly fraught. The principal objection, strongly shared by Washington and London, is Salmond's pledge to rid Scotland of nuclear weapons by closing the Trident submarine bases at Faslane.

But SNP plans for building up an independent Scottish army, air force and navy, initially using assets such as Royal Navy frigates and minesweepers willingly donated by London, while simultaneously delivering a £500m "security dividend" by 2016-17, look like highly disruptive fantasy.

Mariot Leslie, a Scottish former UK ambassador to Nato, argued recently that an independent Scotland would continue to play its role within Nato, and that Nato members would support it. "No ally would wish to interrupt the integrated Nato defence arrangements in the North Sea and north Atlantic – least of all at a time of heightened tension with Russia," Leslie said. But Salmond's plans, whose credibility is not helped by a proposed defence budget of £2.5bn, will involve enormously complex negotiations and risky logistical upheavals. Russia's Vladimir Putin will doubtless be watching with interest.

SNP plans will also require an extraordinary degree of goodwill on behalf of the London government which, in the teeth of an unwanted and hugely expensive separation, might not be forthcoming.

For example, Salmond has valued the UK's overseas properties, including its embassies, at £1.9bn. Scotland's "share" would be worth £150m, which he would use to create a duplicate network of Scottish embassies. Salmond apparently expects this money to be handed over without demure on or before March 2016, the date of independence if it comes.

It is a tough world out there, and getting tougher all the time. For survival, friends and allies are indispensable. The SNP's blithe assumption that an independent Scotland will be speedily and unquestioningly welcomed into a range of other international bodies, including the World Trade Organisation, the OECD, the Council of Europe, and the OSCE, looks optimistic.

So, too, does Salmond's claim that Scotland, with a population of just over five million, can make a big, even unique, impact on international policy on democracy building, climate change, and development issues.

"There are inherent advantages in being a smaller, well-governed, independent state in a rapidly changing world," the SNP's white paper argues.

There are also significant disadvantages in a globalised, inter-connected and highly volatile age. An independent Scotland would be on a par, population-wise, with Lebanon, Slovakia, Kyrgyzstan, El Salvador, Turkmenistan and the Republic of Congo. Truth be told, these countries have little or no say about how the world works. Things happen to them; they don't make things happen. In seeking separation, Scotland risks irrelevance.