Canada, the US, and other countries regularly issue travel alerts, and anyone who travels should get in the habit of checking them before buying tickets. They aren't a joke, they aren't political, and they carry repercussions in terms of whether you'll be bailed out if things go wrong. See travel advisories from the US, Canada and the UK.
The current travel alert for Europe does not warn people against going to Europe; it merely describes an ongoing threat and current concerns by European governments, and suggests that US citizens register with a US travel service. I wouldn't cancel a trip because of it, but it would cause me to keep my ears open for possible developments.
There are times when you can take advantage of non-existent but perceived threats. When Reagan bombed Libya in 1986, I immediately made plans for a European holiday. American tourists were terrified of terrorism in Europe that summer and stayed away in droves. I rented a car for three weeks and did a driving tour to French 3-star restaurants. I could walk in to establishments that normally required at least a year's advance booking, and they were grateful to see me. It was quite a trip - mired only by being doused with radioactive fallout from Chernobyl. But that's another story.