1996 Honda Civic

Shakes or Wobbles problem
1996 Honda Civic 4 cyl Manual 166000 miles

Recently, I had an alignment done along with a new set of tires. Since then whenever I go on the highway the car start wobbling side to side. It feels sort of like I'm being buffetted by strong wind but there is no wind. It remains about the same if I take my hands off the steering wheel.
The shop that did the alignment and put on the tires just said it's the condition of the highway. But that doesn't explain why this started after the alignment.
What can I do to correct this?
Also, does it matter which is done first - the alignment or putting on the new tires?