My idea would be to have a POD at the War of the Spanish Succession. Have the French fare better on the continent, and the Bourbons unite the thrones by force. However, their efforts lead to weaker fights being put up in the colonies and they lose a little more, not to mention that the British, seeing what is about to happen in Europe preemptively seize as many Caribbean islands and such as they can to weaken the French colonial position - maybe the Philippines too, to prevent the French gaining a dominating position in the Indies too early. So you have a pretty uber Franco-Spain now. Somewhere down the line Portugal is weakened and it gradually is brought into the French sphere of influence. It probably would never be annexed, but it could become a satellite. Maybe a personal union with France down the line, it's not so important. Anyway, on to the next step.
On rolls the 18th century. Britain, greatly fearing France's huge chunks of the Americas etc makes increasingly aggressive steps, while France finds that without the sugar islands their new colonial empire doesn't actually aid them at all in being able to fight in the colonies, except for having more ports and a load of gold to create inflation. Gradually the British turn the tide and after another unexpected victory such as Wolfe's Quebec City, the French are forced to cede their North American possessions. Come 1773, similar things to OTL happen but the British react faster or the Americans are less hotheaded or something, and the Americans chose to stay loyal instead of starting the ARW. Albany Plan or somesuch. England's position as the dominant trade position isn't secured yet, but with this event it's jumped the last hurdle. Thus, circumstances aren't conducive to the Revolutionary Wars - mainly 'cos it would mess up my train of thought (and because I'm not a fan of Revolutionary France), even though it might actually help this TL go on. Around 1800 you then get a marrying of the British Princess to a Swedish Prince. In one of those acts of fate, OTL Victoria is stillborn and her mother dies in labour. Edward (her father) remarries but the union proves barren. Come 1837, the now King of Sweden - still a Vasa due to the lack of Napoleonic Wars - inherits the British throne in the same way that so many others have, leading to what is later seen as the British incorporation of Sweden - though Sweden remains a very strong partner in the Union, unlike all of Britain's other accumulations through inheritance.
Skip another generation. Germany isn't like the threatening signs France is making, and a trade union in the style of the Zollverein is enacted, only this time by Austria, in order to bind the German states together. Only Prussia stays out, having dallied with a French alliance a few times, but in the end it is swayed to the Russians. Russia persuades Prussia to make a move, reckoning that France will show benevolent neutrality as it watches Austria be taken down several rungs. They completely misjudge the situation however, and the French ally with Austria, believing this their chance to turn Germany into their sphere of influence while restricting Russia, who they believe a greater threat than Austria. Denmark sides with France and Austria, having seen Prussia eye up Schleswig-Holstein for some time now. Britain, in an attempt to preserve the status quo, sides with Prussia and Russia, believing France's military power too much of a threat. The Vasa king has Swedish troops occupy Norway, which puts up little threat, and British troops occupy Iceland and Greenland, while a colonial war again rages between the UK and France. On the continent, Denmark steps too early and its army is caught away from the French and destroyed very early on. The French quickly march to save it, but in complete disarray the Danish King bottles it and signs a peace, ceding Norway, Iceland and Greenland to Sweden, a little to the concern of the British Parliament who had less aggressive ideas, and Schleswig-Holstein to Prussia. France then turns and marches on Prussia and Russia. The Ottomans get dragged in somehow. The war is closer than expected, with the British causing economic havoc and the Russians scoring some important victories, but at the end of the day the French overcome the Prussian-Russian alliance. The Ottomans are forced to cede virtually all of the Balkans - they lose the rest a few decades later in another unequal fight to prevent the Russians from accessing the Mediterranean through the Bosporus. The British, seeing what is going on, purchase a number of Ottoman islands first, to protect their trade control and to prevent the Austrians or worse, the French, gaining too much. Cyprus, the Ionians and some strategically important and defensively sound Aegean Islands (to give the British a control in the Bosporus passage too) are sold. Austria manages to keep France's grubby mitts out of Germany, mostly, gaining Prussia's west German holdings. Germany is pretty much condemned to Austrian control now. A couple of decades on, Prussia attempts to catch the Austrians off guard and restore the balance, but gets smacked down and the Prussian King gets deposed. Grossdeutschland is now in play. France loses more colonies as the American colonists form their own regular armies for the first time (well...as a temporary measure but it's more than militia) and storms over French Mexico, proclaiming the Manifest Destiny of the American colonists' superiority over French colonies, France pawns them off to Britain to end the war, not really liking the Spanish colonists anyway.
As times change and alliances shift, Russia and Austria drift apart, the former now siding with France against Austria and Britain. Another war sparks between the new alliances. Things go well for France before they suffer a crushing blow in a battle and their ability to fight is reduced for several critical months. Austria then turns on Russia, having set up Poland as effectively a buffer state previously, marching through and getting the Russian invasion right for once - mainly through having restrained campaign goals, and not trying to fight over winter. This is helped by the Swedish ability to march over land through Finland to siege Saint Petersburg and Moscow relatively quickly. Russia is compelled to jettison much of its territories west and south of Moscow, simply as it has no other option. Utterly humiliated, they turn instead to their new conflicts with Japan, but these don't go so well either and Russia is clearly a fading power.
Well that almost does it. Just need to engineer some event to make Russia fall under one country's sway.
Wow...can't believe I've just typed for so long.