Not even slightly right. Capitalism is based on free and voluntary trade, in a truly capitalistic society (like the US used to be a long time ago) anyone can compete to offer services, in the US there was a period where the government stepped in and created a monopoly in the phone system and internet provisioning by bringing in regulations and taking control.
Monopolies can only be sustained when one company has an unfair advantage over the others such as government enforced rules and regulations that favour one over the other, they're almost never seen in actual free markets. Never the less monopolies always involve force from some institution like a government and so are always bad because no one should have the right to force anyone else to do anything, that's the opposite of capitalism.
Sure the US is bigger but that's not really relevant at all, more people just mean more revenue since ISPs are in the business of making money. The problem over there is the loss of the free market, the UK had exactly the same problem and BT our main provider had a monopoly, now the physical lines are opened up for anyone to use and we have a really healthy broadband market which is highly competitive and it drives prices down.
The underlying problem still present in most peoples thinking however is this idea that somehow bandwidth is cheap or even free, when it's quite the opposite, it's expensive and provisioning a lot of it costs a lot of money and when you pay for a cheap connection you sacrifice certain things like having data caps.
No, monopolies absolutely occur on their own in free markets as well. Plenty of instances of companies that gained monopoly power without government regulation (in fact due to the lack of it actually), just by controlling all the means they can (there were tons of this happening in the early 1900s). They were actually a lot more common but then government regulation worked to reduce it. Obviously that's not always been perfect either, but the only reason that monopolies tend to exist now is because in certain markets there's benefits that outweigh the negatives for various reasons (when it comes to things like utilities, the only way to have actual free market competition is if the government sets up the infrastructure as it's not feasible to have tons of companies putting in their own; plus there would be so much turnover in companies that it could end up with worse service or none at all which are bigger problems). Point is, regulations are what has helped limit monopolies from being more common.
It is true that government did setup monopolies in the US with regards to communications although it's not quite how you act like it is. They allowed if a company put in the infrastructure that they would gain sole right to provide service. Which that actually worked pretty well for a while as it gave incentive for companies to put in service back when none existed there. However over time fewer and fewer companies were actually in control until it culminated in Bell's dominance (which was broken up but has effectively built back up, now we have AT&T and Verizon). Then we saw the rise of cable which operated similarly. The issue is that governments didn't put in term limits for monopoly control, and companies got so used to it that they've done about as much as possible to not compete.
But that's also why your whole argument is horribly flawed in that you act like ISPs can't afford to provide consistent bandwidth for users which is just wrong. Fact is we already paid for the infrastructure via government subsidies, tax breaks, and also directly by paying excessive amounts for service. Meaning that you say it's so expensive for them to be able to provide adequate bandwidth, but what we're trying to tell you is that we already paid and continue to do so and yet they're trying to add bandwidth caps and other things to try and charge more for the service they claimed they were already supplying, while they simultaneously advertise how great their networks are (but then are complaining to the FCC about how much they're hurting, all while their profits continue to climb and they continue to try to further expand their dominance by mergers and acquisitions).
If an ISP is losing money on people that download 300GB a month then they're horribly run as it absolutely does not cost them that much to provide that. If
all of their customers started doing that then yes it would be different, but they aren't, not even close. Sure it costs more to guarantee bandwidth and speed, which is partly why those services that do cost a lot, but that cost is not that high just because of the bandwidth provisioning (it's not even close). It costs that much because it pays for guaranteed service as in if there's a line that goes down they go and get it fixed ASAP, as well as other features that ensure no downtime for the customer. The market for that is also a lot smaller meaning much higher prices, that's simple economies of scale.
Oh and also, regulations are actually an integral part of the internet. Now discussions about what those should be and who should be in control of them is a different issue, but acting like everything would be great without any is just nonsense. Look at technology in general, it's been necessary to have to come up with standards and regulations in order to keep things open and accessible. Coming up with them actually helped the growth of the internet. Oh and surely we don't have to remind you who actually got the internet started (a government entity).
Also you do realize it was regulation that opened up the internet in the UK, right? The government instituted local loop unbundling, which forced companies to have to lease their lines to anyone, enabling ISPs to crop up and compete just on service. Without regulation those companies in a free market would have been able to say no its their line.
In the US in the late 90s, the FCC actually had also done that but with regards to the telephone lines (since they have been paid for many times over by that point) and for a while we saw really good competition in dial-up and even DSL. They actually got rid of it with regards to DSL several years back which is why DSL went to crap here. Now, we have issues because two of the major phone line providers (AT&T and Verizon) are also the two major cellular providers and cellular and guess which one is more profitable (even though they're also spending tons of money on the networks)? Guess what's happening? They're letting phone lines rot and trying to push people to wireless service.
With regards to bandwidth caps, they absolutely are not about doing what you said (spreading out usage over time). If they were they would just say that during times of high network utilization that they will throttle speeds (and just cap everyone at a certain speed) and they would work with the people using high amounts of bandwidth to see if they could adjust when they utilized it to lessen their load for peak times. But they don't, they generally send warnings to the user that they'll terminate their service and/or try to get them to upgrade to their more expensive commercial services. Or they decided to do the caps so they could just charge large fees for overages. They have outright admitted this to the FCC (that its not about congestion, they just feel they should get to charge more for more use like they get to on mobile). Which mobile carriers got caught redhanded throttling unlimited data users, at first claiming they only did it when the network was congested, but then they admitted that had nothing to do with it. Even having a soft cap where they just throttle your speed once you go beyond it doesn't really do what you claim a cap is there for as bandwidth consumption tends to not be so consistent so its not like its something end users could fix easily so they basically would have to just plain drastically reduce their overall use or switch (which often isn't possible or is only to another company where they'll likely have the same problems). The other thing is that they've rebuffed offers that would help lower their network issues (Netflix offered to put servers directly on their networks, for free mind you, so that it would both limit congestion at the interlinks between the ISPs and the rest of the network and provide faster speed and thus better quality of Netflix content for the ISPs customers, who by the way already payed the ISP for the bandwidth they're requesting from Netflix; the major ones flatly refused this and demanded that Netflix pay them for direct connection).