I'm not any more nervous than travelling to the US now than I ever was. If anything, people are more watchful of suspicous behaviour and there's tighter (though not perfect) security at the borders and airports.
I'd be more worried about a car-jacking, mugging, or getting in a run-of-the-mill car accident during my trip.
After my last flight from London (UK not Ontario) to Vancouver, my flight was quarrantined and a few 'suspicious' men were being questioned by customs officers. Scary? Maybe. But at least the Customs officials are paying attention and not daydreaming about what to cook for dinner.
I really believe in seeing things as they 'are' at the moment and not 'worse than they are'. I plan to blissfully (ignorance IS bliss) continue to plan my trip, dream of sunshine, a large mouse and fireworks.
If a war interrupts that, there's nothing I can do about it.
Enjoy your vacation planning!