Getting rid of the USA, or making it more oligarchic, is pretty much essential; a powerful representative-democratic state well-positioned to rule much of a whole continent is too strong to be easily got rid of. Getting rid of early constitutionalism in Europe is also probably best; it's easier to strangle representative democracy in the cradle than to have it arise and then die away.
I would argue that the development of representative democracy was a historical fluke of OTL rather than some kind of inevitable march of progress. The idea of institutions initially created to serve the interests of the nobility against the monarchy expanding to not only give a bit of representation to the wealthy middle classes but be dominated by them is the key thing that has to be got rid of; once that has happened, it's not so much of a dramatic change to gradually reduce the amount of wealth a commoner needs to be represented. But that development, with wealthy lowborn people getting into and taking over institutions created for the highborn and siding with them against royal power, was hardly inevitable; this is why I so despise it when people create AHs where there's a traditional noble/royal state which "reforms" and automatically becomes a representative-democratic state, as if this is just "what happens" as expected. Even for most of the 19th century in OTL, even in the United Kingdom, the House of Lords was the house that supplied the leader of the country, not the House of Commons. Have the nobility be more strongly represented than representatives of the boroughs in early councils/assemblies/parliaments at the time of the Industrial Revolution, cracking down on those for fear of irrelevance, and we could reasonably see the development of centralised bureaucracy under royal control be supported by the rising middle classes (well, upper-middle classes—principally wealthy merchants, factory-owners and those of that sort) as the way for them to be able to achieve positions of power, as opposed to aristocratic-dominated parliaments. Without existing representative-democratic states, and with the general tendency of revolutions to be dominated by charismatic revolutionary leaders who can easily choose authoritarianism, I don't think such an ideology is likely to spring out of the blue.
If one wants a later PoD where representative democracy exists and is powerful, but then fails, it's probably still necessary to avoid the existence of the USA—stable representative-democratic states aren't useful here. Economic crises can lead to the rise of authoritarian governments, as we saw in much of Europe in the inter-war era. Have a big WW2-esque war be won by an authoritarian alliance and one can easily imagine the developed world be dominated by authoritarian left-wing or authoritarian right-wing regimes, rather than representative democracies. If the USA had stayed isolationist, this would have been the case for most of Europe even in OTL, dominated by Stalinism after the defeat of National Socialism. Make North America as poor and riddled with oligarchy and instability as OTL South America, and make any parts of the Americas that are as developed as Europe not have the exceptionally long and stable representative-democratic tradition that the USA has (which isn't too hard—the USA is the exception rather than the rule) and it shouldn't be too hard to have a developed world where representative democracy is close to non-existent and therefore a developing world where, upon gaining independence, leaders have no particular incentive to create representative-democratic institutions. Even if you want to keep the USA, just give it enough economic trouble and prevent the early death of the socialist movement, so you can get some right-wing dictatorship (with a MacArthur-esque figure in charge, backed by organised religion and big business figures) to take power out of fear of socialism in a 'failure of democracy' when there was electoral gridlock or fear of leftist electoral victory.
The victory of the USA's political tradition throughout much of the world, driven by the Second World War and the Cold War, is hardly an inevitability.
