Yup trade in your 5 or 6 Houses for 20 or so states but that isn't all. The Cameron society that gave us Neo-Feudal Lords, Mechwarriors, their honor code, and a limited warfare setting is likely a goner. The universe you get maybe far more "realistic" than the "fantastic" BattleTech we all love.
The large states had formed in response to James McKenna's campaigns, not the rise of the Camerons, so I think the 10 states would have still formed in similar ways.
Of the ten large states in the 26th century, only the Capellan Confederation, Outworlds Alliance and Magistracy of Canopus were created after the proposed election. Given that the Capellan Confederation formed in response to being caught between the expansionist FWL and FS (particularly the latter) it's likely that the Capellans will unite more or less per canon although if House Nellas is more aggressive than House Cameron it's possible that the Ducy of Liao might have been conquered by the Terran Hegemony, which would throw quite a wrench into that chain of events.
The OWA and MoC would almost certainly be butterflied depending on the Nellas actions through the Age of War although it's entirely plausible that similar states might emerge.
One chain of events is:-
The Nellas succeed in annexing the Duchy of Liao; leading to Franco Liao not attending the St Andre Conference; leading to the Capellan Confederation; leading to Reynard Davion successfully seizing control of Capella and by extension the Capellan Commonality. A scramble by the TH, FWL and FS to carve up the Capellan sector could readily kick off the Age of War thirty years earlier.
Other consequences of this would be that it might well avert the first clash between the Taurians and the Federated Suns (which was inadvertantly sparked by the Capellan Confederation) and avert the entire Magistracy of Canopus since the campaigns that disenchanted Kossandra Centrella would take place under different leadership. Finally, with the Terrans looking 'south' that might grant more freedom of action to the Lyrans and Draconians. There's no knowing what
that could cause.