The British political class, like much of the British media, remains foolishly obsessed with America to the exclusion of all other foreign countries. As a result, both refuse to pay consistent attention to German politics, or indeed to the internal politics of any other European country at all. So the news that Angela Merkel may not, after all, continue in office as Germany’s chancellor will have come as a rude shock to many of them.

The British have always blithely assumed that Merkel would somehow ride to the UK’s rescue over Brexit like the Prussians at the battle of Waterloo. David Cameron thought this would happen in the negotiations preceding the referendum in 2015-16. Now Theresa May, and certainly David Davis, seem to have a similar hope over Brexit. It is a foolish error.

Like most German politicians, Merkel is not actively anti-British in any way. She would certainly welcome a Britain that was a committed ally in Europe. But that’s not the Britain that is on offer, the more’s the pity.

The truth has always been that Merkel has more pressing priorities at home than Brexit, and more reliable allies in Europe than Britain. Now that coalition talks between Merkel’s CDU-CSU Christian Democrats, the free market liberal FDP and the Greens have broken down, however, the prospect that Merkel may not even be there as the Brexit talks reach their climax is a real one.

Merkel will still be chancellor when Theresa May goes to Brussels on 14 December for the EU summit that must decide if “sufficient progress” has been made in the Brexit talks. So she will still matter. But the idea that Merkel will or could somehow magic an 11th-hour solution favourable to Britain is simply for the birds. It misunderstands – as too many in the Conservative party do, taking their cue from the insouciant Davis – the nature of the process that is supposed to be taking place.

In these Brexit talks, Germany has the influence that comes from being Europe’s most important country, but the process within which it is exercised is essentially a legal one, laid down by treaty. The British have never understood that they are the appellant not the defendant in the Brexit talks: it’s Britain that wants to leave, so the UK, not the EU, has to make the big moves towards compromise deals.

But this error is compounded by another: the conviction that Germany will go significantly out of its way to help Brexit Britain. Germany’s overriding concern is that the EU must survive, cohere and strengthen in the face of testing events. The big impact on the European level of the coalition talks breakdown is that it sets back Emmanuel Macron’s hopes of persuading Germany to reform eurozone priorities and structures.

Neither France nor Germany has any long-term political interest in assisting Britain to make a favourable bespoke deal that could become both a precedent and a catalyst towards divergence within the EU. As German business leaders told Davis in Berlin last week, they want Britain to make the moves that matter, not to be offered a special deal that suits Eurosceptics.

In any case, Brexit is largely irrelevant to the coalition talks in Berlin. A senior German official recently told me that Brexit was about the eighth or ninth issue on Merkel’s to-do list in foreign affairs, never mind the domestic politics that are any leader’s inevitable priority. As an illustration, the issues that matter in the talks that have just failed were: first, migration policy; second, the future of coal; and third, financial transfers from the regions of the former West Germany to those of the former East Germany.

Germany is a stable country with built-in constitutional safeguards that derive from the determination to avoid the instabilities of the past. In Britain the failure of talks would create a frantic domestic political crisis that would have to solved by next weekend at the latest. Germany has weeks and months to sort out whether it can form a government. During this time Merkel will remain in charge.

But Germany is in a political territory without maps. It has no postwar tradition of minority governments. Yet there are now six parties in the Bundestag, which has the effect that coalitions are even more inevitable than in the past, for all their difficulty. It is not impossible that some in the opposition Social Democratic party will be open to overtures to rethink the party’s refusal to continue in government under Merkel. But that looks a long shot.

The great unknown in future elections is whether Germans decide they have looked over the precipice of a six-party Bundestag, have seen the ultra-right Alternative für Deutschland in parliament, and will now turn once more to Merkel and the Christian Democrats as the best guarantee of stability.

The immediate effect of the break-up of talks will be to weaken the FDP, which is taking the blame for the failure. But the longer-term issue is whether Merkel can restore the Christian Democrats at the heart of German politics. Compared with that, Brexit looks a distinctly second-order priority.

• Martin Kettle is a Guardian columnist