If the US has occasion to go to war every ten years, who do you think it will be next?

Iran is

currently

the biggest threat to our people.

We know that they have been sponsoring international terrorism

including occasional terrorism against U.S. targets in the Middle East

for years.

They are the most likely to drive us to the point where we feel war is a practical solution.

Of course, there's no way to tell the future.

For example: what if the Taliban managed to retake Afghanistan and began to again sponsor terrorist actions against U.S. targets?

The danger of Iran's efforts against the U.S. would seem paltry by comparison, and our next war would probably be in Afghanistan.

The biggest, most complicated, most expensive wars have usually, (though not always),  started under Democrats.  It's they only way they know how to boost our economy.  Check all the wars we've been pulled into since, let's say, 1890 and then look at which party rule coincided with most. 

I think Syria probably.

oh, the Middle East is always the top candidate