By Greg Dobbs*

American intelligence says that terrorists from the Yemeni group widely considered the most dangerously anti-Western of all the al-Qaeda spinoffs, al-Qaeda in the Arabian Peninsula, have snuck into Saudi Arabia to position themselves to attack the kingdom. And although our alliance with the Saudis is based only on mutual interests — which realistically means mutual enemies — an attack on Saudi Arabia is as good as an attack on us, because with so much oil so easy to get at, Saudi leaders influence the global price of oil and thus the economy — and therefore the stability — of the planet. Unless, of course, they are thrown off their feet and someone far more hostile stands in their shoes.

And now, al-Qaeda might not be the only force with its eyes on that prize. An Iran-backed sect in Yemen, the Houthi Militia (all Shiites), has moved to the front. Which means al-Qaeda in the Arabian Peninsula (mainly Sunnis) no longer has the whole place to itself. Adding to the mayhem, the Islamic State reportedly is elbowing its own way into the chaos. Is it plausible that the self-proclaimed "caliph" of the Islamic State — by his lights, the leader of all Muslims — has designs on the holiest domain in his faith?

All told, this can't be good. Between religious, tribal and territorial objectives, each of these groups probably will fight fiercely for a piece of the spoils. Viewed in a vacuum, nothing would make America happier. But warfare among terror groups in a place like Yemen has its downside, not only because it's likely to ravage the nation, but also because in a case like this (unlike Syria, where the beleaguered government has muscle that the Yemeni government never had), someone's likely to win. Then that victor would stand taller, and stronger, and probably meaner than ever.

Which makes the upheaval in Yemen an even more potent potential threat, not just toward the sands of Saudi Arabia, but also toward the American homeland. The Yemeni intelligence that helped us fight terrorism on the Arabian Peninsula now might end up in the hands of the terrorists themselves, which forces us to suspend that fight. Which means three factions hostile to our interests would have fairly free reign.

Sure, they don't like each other, but when anti-government demonstrators in Yemen last week chanted "Death to America," they voiced a common passion. That makes them a collective threat. Another impermeable terrorist refuge might just have been born.

Which is why we're in trouble.

*Greg Dobbs of Evergreen was a correspondent for ABC News for 23 years, then for HDNet television's "World Report."