Christina-
Unless the UAV's fly at low altitudes, they won't interfere with air traffic in the area.
I live in North Central MT, about 10 miles south of the border. The area along the border, from the Rocky Mountain Front to the North Dakota border, is about 400 miles long. There are no roads, towns, and very few occupied dwellings within 10-20 miles of the border over most of that stretch. The only roads that are near the border are the roads that lead to the part-time ports of entry, which are scattered out about every 40-50 miles along the border. US Highway 2 runs parallel to the border, about 30-40 miles to the south. Between the highway and the border there is about as little human activity as any place in the Lower 48. In that entire area, about 15-20,000 square miles, there is a permanent population of, perhaps, 2,000 people. Cattle outnumber humans 50:1. West of Hogeland,(Pop. 15), near which I live, there isn't another town of any size for almost 200 miles. There are no airports with scheduled air service near the border, and the great circle routes which cross through here are up in the flight levels.
There are quite a few airplanes in this area. Not too surprising considering the size of the country, and the distances involved. We locals seldom fly near the border, and seldom over 500 ft AGL. We seldom fly into Canada, as there are no longer airports of entry on either side of the border close enough to make travel by light plane practical, unless the destination is hundreds of miles away.
UAV's could cut down on the massive Border Patrol presence on the ground here since 9/11. Pork barrel politics being what they are, however, we will probably have hundreds of BP officers, plus air patrols.
The border region of the northern plains is a very isolated place. It would be easy for someone to slip across undetected, except for one thing: Rural people, in remote areas, are keenly aware of any activity which appears different from the routines they are accustomed to. If one strange vehicle passes by, the phones and business band radios light up. "Did you see that green van going by the old Jackson place? Wonder who that was. Which way did they turn? I'm gonna call my niece who works at the sheriff's department and see what she knows".
Nosy neighbors are a more effective deterrent than all the high-tech wizardry the Dep't. of Homeland Security can dream up. Trust me.
Mark