In the US, you can do whatever the heck you want. We have extremely liberal free speech laws in ways that very few countries do. The limits on free speech tend to only be threats or ‘incitement’ which is basically you telling someone else to hurt a third party (“Why don’t you guys go over there and kill that dude.” It has to be fairly specific. If you were to simply say, “Politician A deserves to die.” You’re probably in the clear. If you were to say “Let’s go kill Politician A.” you’re going to get a visit from the Secret Service.), causing a panic (Yelling fire in a crowded theater.), fraud (I think we know that one.) and libel/slander (although those are both notoriously difficult to prove.) Otherwise, it’s pretty much whatever you want. The limits on opinion speech (which is what a pro-terrorism statue would be) are pretty much non-existent. If you want to put up a giant statue of Osama bin Laden that says “The Greatest Man Ever. We need sharia now. The kuffar will kneel before our greatness.” The neighbors might get mad, but you’d be within your legal rights (Barring deed restrictions and possible safety violations if your statue was poorly designed.)
This freedom of speech is why we have KKK rallies and Nazi parades and all manner of distasteful displays. There is a very strong cultural undercurrent in the US that says you can express any opinion no matter how hateful or distasteful without fear of governmental retribution. There is even a distaste for police presence near where you are making your speech displays for fear of it being intimidation. That’s one of the reasons we have things like Charlottesville because police don’t really know how to act. If they set up a barricade around a racist rally, is that for protection or is it intimidation or is it blocking people’s access to hear the speech? In the US, those are issues that are difficult to deal with.
Personally, I like our free speech laws. It makes me very uncomfortable when I hear about anti-Nazi speech legislation in Europe. I get why they do it, but as an American, it strikes me as weird and oppressive.
There are numerous monuments to the IRA in Northern Ireland, on both public and private land, so that’s a ‘yes’ from the UK.
I’m not so sure about how an ISIS statue might go down.
OK, that point I’ll concede. 
General Curtis LeMay ordered extensive bombing of civilians in Japan 1945, Korea 1950-1953 and to lesser extent Southeast Asia 1965-1973.
Thank you – indeed USA has a much broader definition of Free Speech then most nations.
In UK a person can be imprisoned for a rude post on a forum.
Okaaay