You're really describing Republicans rather than Nationalists per se as one is usually much more balanced than the other. Although I note most Republicans like to call themselves Nationalists these days which isn't surprising because it doesn't carry to heavy baggage Republican does.
Belfast's similarities to Glasgow and northern English cities is actually deeper than simply architecture or layout.
As these tidbits from the National Archives Of Ireland demonstrates:
"Even the northern industrial towns of England, with which Belfast shared so many similarities, could not match a city which became the fastest growing urban area in the United Kingdom of Great Britain and Ireland."
And:
"Social life in Belfast was markedly similar to that in the northern industrial towns of England."
And:
"The professional soccer leagues of northern England were replicated in the working class culture of Belfast: thousands of men in flat caps poured into soccer grounds on Saturday afternoons to attend matches."
So, social life was pretty similar as well. The impact of the decline of heat industry was the same in Belfast as in Glasgow and Sheffield, for example. The connections between Belfast and other British cities is historically clear. Indeed, Belfast was known as Linenopolis while Manchester was Cottonopolis.
It shouldn't be a surprise that British trade also brought British social norms, activities and past times with it to Belfast. The description of Belfast as a British city stands. I've certainly seen Nationalists refer to Belfast as being a British city in contrast to Dublin being much more an Irish city too.