There's a related discussion here. Domestically, I would say that Scots did, even lending England a dynasty and later sharing in the wider imperial venture, size having been a limit to earlier expansion. Ireland however never achieved national unity before the start of Anglo-Norman domination, and the character of English rule was unconducive to its later development.

The greatest factor in Ireland's disunity was not any sort of isolation , as Irish merchants traded as far as Egypt . It was the institutions of Irish Society that prevented a consolidation of power. Brehon law, although remarkable for it's time period was used by all of the Irish kingdoms and so, by its succesion law, inherited land was repartitioned to the Derbfhine(people with a common great grandfather), and in the high middle ages the Gelfhine (The agnatic line). This meant that land was constantly divided , limiting the momentum of large dynasties súch as the Uí Neill.

Secondly, 'Feudalism' was never adopted by the Gaels in Ireland , instead was a system known as célsine , translating to clientship. For the High King especially , Authority was suzerain rather thán direct. In comparison to the Norman system of government which was remarkably effecient, Norman england could effectively raise more soldiers due to their centralised governments , in contrast to the decentralised and fractured Gaelic kingdoms to the west.

However , there were a number of occasions where the Gaelic Kingdoms of Ireland and Scotland nearly rose to power in a way that would rival england , such as the De Brus Campaign in Ireland(1315-1318) and the Nine Years war(1594)

One could argue for two key reasons.

First, the Irish and Scottish lands are not as resourceful as those of England - especially southern England, the land of which offered opportunity for increasingly intensive agriculture from the Iron Age on. Ireland has a lot of copper and gold in the Bronze Age, but this was quickly tapped out and by the Iron Age it was a backwater.

Two, geography. England's proximity to the Continent meant that there was a lot of invasion, immigration, cultural co-mingling, and diffusion of technology. This arguably put the people in charge of that area in an increasingly stronger position to subjugate the Irish and Scots.