It's not quite so simple. The whole point of the 1996 Telecom Act was to get rid of the legal monopolies and get the government out of the business of regulating them. What we have now are incumbents not monopolists. However, in a low-margin industry (Verizon's wireline operating margin is 2-5%) with enormous capital costs, that's kind of a theoretical distinction.

ILEC's still have a monopoly on copper runs in most jurisdictions afaik.

They own the copper runs. But if you want to compete with them by building your own infrastructure you're allowed to do that. In most places, it's the power companies that own the utility lines, not the telcos. The problem is it's not worth anybody's while to do it to earn 3-5% return.

A monopoly doesn't require that other people be legally prohibited from competing (if they are, that's a granted-by-law monopoly), it requires that you have sufficient dominance in some market as to exercise pricing power within that market.

"In the US, many telecoms operate as a legal monopoly."

I assumed we were talking about ^^^.

I'm not being pedantic about the distinction. If you're of a libertarian bent, there is a big difference between legal and de-facto monopolists.

So, there are no smaller telecom companies (internet providers) in the US?

Tons, but odds are if you select 100 Americans at random, 95 of them won't have access to a smaller ISP than Verizon or Comcast.