From The Penguin History Of Latin America, by Edwin Williamson (Penguin, 2003), Kindle pp. 208-209:
It was generally recognized in Portugal that Brazil was the engine of the imperial economy. Though Portugal might have reversed her trade deficit with Britain, it was only because she was herself in chronic deficit with her largest colony. The imbalance, however, did not lead to political frustration in Brazil. The Portuguese had been conspicuously successful in creating a unitary sense of empire in which the colonial élites could strongly identify with the mother country. In contrast to Spanish America, there was no great resentment against peninsular Portuguese: there existed little by way of a separate Brazilian culture for the élite; the involvement of sugar planters in the export-economy made for a common interest with Portuguese merchants, slave-traders and royal officials; finally, the massive presence of Africans and mulattos reinforced the identification of white Brazilians with their European cousins (family ties were, indeed, close).
The political value of this unitary sense of empire was well understood by Portuguese statesmen. Pombal, for instance, was careful not to alienate the Brazilian élites by his reforms. Posts in the bureaucracy and in the newly founded militias were open to Brazilians; local oligarchies were allowed to invest in the monopoly companies; the introduction of new crops into hitherto unsettled areas and the general expansion and liberalization of trade were designed to favour American as much as European Portuguese. Even the expulsion of the Jesuits, who had always opposed the white settlers’ Indian slaving and occupation of native lands, met with Brazilian approval – the large, well-managed estates of the Jesuits, as well as the Indian labour released by the destruction of the missions, provided excellent economic opportunities for wealthy merchants and planters. Brazil was considered to be fully a part of Portugal, even though it happened to be situated on the other side of the Atlantic Ocean; so much so, that the possibility of transferring the imperial court to Brazil in a time of peril had been mooted in Lisbon as early as the middle of the seventeenth century.
The American and French revolutions were to plunge all of Europe, Portugal included, into ideological and military turmoil.