whoever wakes in England Sees, some morning, unaware, That the lowest boughs and the brushwood sheaf Round the elm-tree bole are in tiny leaf, While the chaffinch sings on the orchard bough In England—now! (3-8)
We get the word "England" twice in just six lines here. The speaker is really driving home that this beautiful scene is not just his own personal memory; it's a particular vision of a particular country.
And after April, when May follows, And the whitethroat builds, and all the swallows! Hark, where my blossomed pear-tree in the hedge Leans to the field and scatters on the clover (9-12)
We are treated to more detail about the natural beauty of England here, but we're also getting a selective vision of the country. The poem leaves out any mention of city life, factory smoke, class struggle, imperial conquest—anything, basically, that might mar the image of England in the reader's mind.
That's the wise thrush; he sings each song twice over, Lest you should think he never could recapture The first fine careless rapture! (14-16)
Heck, even the birds can't believe how awesome it is to be in England. The "rapture" of the thrush here reflects a kind of overwhelming joy that's closely associated with both being at home, but also with being on English soil—or in an English tree, anyway.
And though the fields look rough with hoary dew, All will be gay when noontide wakes anew The buttercups, the little children's dower (17-19)
The speaker's description of the scenery is given an emotional punch when he mentions "the little children" in the lines. Those sweet, innocent creatures are the beneficiaries of a "dower," an inheritance, of buttercups. While those may be hard to spend, it's clear that what's really being passed down is a kind of patriotic gift: access to the beauty of the English countryside.