The difference many are mentioning is urban vs rural views. Rural is the natural human situation. Humans going back thousands of years ideally had a piece of land that created enough space for them to be self reliant in growing or raising food, creating defensible space, and having a piece of the world to shape as their own.
This was the situation when the Constitution was drafted.
This situation better supports freedom as people spend a significant part of their time in a space that has far less impact on others, and so others are more inclined to support their freedom to do what they want in that space and in life in general.
Modern urbanized lifestyles are more efficient, giant mass scale farming produces more for less, and people packed into small spaces where they have little more than sleeping and cooking quarters gives the most room to grow the population (and government always wants a bigger population to support the pyramid scheme of government which does better with more people to pay for the prior generations than were in the prior generation.) The ideal of many city planners is to have few people driving and instead using mass transit, and living in living spaces that are as small as possible to fit as many people in the available space as possible. With large homes made for those with enough money only to better acquire property taxes through more expensive home values, often still designing them to use limited valuable acreage. This is reflected in what they allow developers to build and do, and developers want maximum returns too.
The giant homes that take up almost the whole lot and end ten feet from the neighbor accomplish taking the most property taxes from the resident for a given amount of used land. So there is strong motivations for how cities progress and develop and it is contrary to what was the natural situation most humans lived in for thousands of years.
City living is not normal. Walking beside random strangers and sharing close space with people you don't know regularly within arms distance is contrary to safety and human etiquette going back for most of human history. This situation causes people to want to better control those people they don't know or understand they share close space with on the street, on the subway or bus, in the hallways of their apartment building, etc. Combine this with the denser communities resulting in the crimes and problems seeming more common than they even are as the high density means every problem has many more neighbors that feel close to where it happened.
Step in the local government trying to better control the population and those fears turn into far more limited rights in dense urban areas as the local government typically is able to restrict the population with more people seeing the erosion of their rights as a positive in giving a greater illusion of safety. The density also means a higher tax paying density, which gives a bigger budget to a more extensive legal and law enforcement system, and while it might not be much greater per capita, it still means a much larger force exerting control on the population.
The other huge factor is one we don't discuss trying to stay firearm oriented in a way that is most inclusive to all as if firearm rights are in their own vacuum and not primarily impacted by things that have little to do with firearm use or misuse. (Why do you think we can do so well with statistics.)
We for most of our history were more homogeneous in spite of what we are all taught of our diversity in government mandated curriculum. The more homogeneous a population the lower its crime and other problems when adjusted for income etc Anyone not being politically correct can see most of our troubles have come from trying to integrate very different cultures and communities that support very different things. When you have a whole subculture or multiple thriving subcultures that do not respect aspects of the law or the culture or morals imposed on them by other aspects of society it becomes normal to live contrary to the desires of the rest of the population, including doing illegal things routinely that are laws imposed by others outside of the subculture. This creates a general apathy towards tradition, and while there is many things that could be improved in tradition, it is tradition because it worked well for a long time and includes the wisdom earned by prior generations. When you throw it out the window you gain problems that were not even requiring resources to deal with previously.
The differences between most of the European immigrants were quite minor in spite of the big deals made about them. Most were from Western Europe. People coming from many parts of Europe came from similar backgrounds, shared similar values, morals, views, religion etc And people stood strong for their views. Today we have trained the generations since the civil rights era to be more and more accepting of everything contrary or different and to even celebrate abnormal as a positive. Well that sounds nice, but the result is a society where everyone is on a different page, and creating their own separate sphere. Well the sphere of some is very different than others, and it impacts our ability to rely on our neighbors or share the same issues.
The reduced time families spend together, longer work hours on average, longer commutes for those not choosing to live in the dense cities where most jobs tend to be located, both parents working as a result of two incomes of mid and low level being required most places, and digital entertainment also promoting the separate spheres as everyone can spend their own separate time watching their own separate things further promoting only the views of the sphere they live in. Most teens would rather be with their friends than family and that has not changed, but when with family they used to actually be with family. Today they are with who they want to be on their phone and most people are less invested in the moment. Employers also rarely used to bother an employee off the clock, and if they wanted to communicate something left a message on the answering machine that would be viewed once or twice a day. So personal time was personal time and work time was work time, yet respect for that has eroded now that everyone carries personal phones.
All of these things are eroding our nation, while we at the same time import massive amounts of immigrants, pretending the various people from anywhere in the world are the same and bringing them in fast tracked to citizenship if they benefit an employer with valuable skills, not to mention the unsecured border made worse by policies in places like California that give more benefits to descendants of illegals than even their own citizens.
We need a stable solid population that shares a culture for more people to view things similarly and to have similar problems that can be best addressed rather than very unique and different problems as a result of being so different.
Too much diversity always leads to Balkanization and makes subcultures that work against the mainstream culture. That leads to more bureaucratic control in an attempt to keeps things working, and increased control usually includes decreasing the power wielded by the average citizen which doesn't go well for firearm rights.