My personal advice would be yes.

I don't think credit pulls ding your credit score by that much, a few points maybe.

The US card is Barclays', so you're not going to the well too often with any particular issuer.

A couple of things to consider:

a) US usually runs a promotion in the fall called "Grand Slam" (although there is speculation they might not this year) which offers points for certain partner activities, one of which might be getting a US credit card. (I know that actually using a card is.) You might want to check the USAir board and see if you can get enough partner activities to get some miles that way.

b) There are numerous reports of people getting a bonus offer of 15,000 points for spending either $750 or $1250 a month in each of 3 consecutive months. (I got this offer once for myself and once for my wife.) In my case the offer came about 2-4 months after getting the card. If your spend is seasonal, you might want to take this possibility into account.