I think they'd be quite useful if your house is robbed while you're there. I know I'd feel more comfortable having one in my home.
That said, the gun laws in the US are insane. It needs regulation and it baffles me to see so many people so passionately against the idea. The fact that assigning armed security guards to schools is seen as a viable alternative to restricting gun access is hilarious to me as an outsider, but were I a citizen of the US I'd be horrified at the country's attitude.