As someone who primarily does British history, it has always seemed odd that US history would adopt this regnal period (and no other, to my knowledge; I never hear about Edwardian America). What's going on there?
Can you provide some examples of usage you've seen? I haven't seen much use of "Victorian period" in reference to purely American events - usually the parts of her reign are separated into antebellum, civil war, and reconstruction (especially in the south).
It's funny this popped up just as I started researching a similar topic after reading the last chapter of "British North America in the Seventeenth and Eighteenth Century " Which is a companion to the Oxford History of the British Empire. I should say that ending chapter Bibliography and Selected readings if you are interested in this would probably be more useful than me as my focus is on British North American Colonies and their relationship and interplay in the greater British State and Empire during 17th and 18th century.
Victorian America is a shorter period than Victorian era of Great Britain. It's pretty much the last half of Queen Victoria's reign starting after the end of Civil War in the US . This was a period where especially on the East Coast people started to look back to Britain and there was an increase cultural exchange between the US and Great Britain in Ideas as well as Architecture. This is different than the relationship between the US and Great Britain before the Civil War where the influence was one could say more one-sided, A.G. Hopkins for example characterized the period of 1783-1861 as the US still being essentially and Honorary Dominion even after political independence from Great Britain. because of Developments after the Civil War though America gained a more equal footing politically with Great Britain. More could be said on the topic especially the interesting relationship of US and Queen Victoria for example with the visiting of the Prince of Wales right before the outbreak of the civil war but this isn't my expertise and so I'm only comfortable painting a broad picture. This is my first time posting in Ask Historians so I'm a bit nervous I might mess it up I typically only respond on history Reddit.
Citations
A.G. HOPKINS, "The United States, 1783-1861: Britain's Honorary Dominion?" Britain and the World,IV (2011), pp. 232-46.
DANIEl WALKER HOWE, "American Victorianism as Culture," American Quarterly ' XXVII (1975), pp.507-32.
ELISA TARMARKIN, Anglophilia: Deference,Devotion, and Antebellum America (Chicago, 2008).