Not a good idea at all.
For a start, the VAT rate in Switzerland is 7.6%. You then have to take into consideration the conversion charges from US $ to CHF and the charges that you will incur in order to get your VAT refund.
Nor is Switzerland a particularly inexpensive country in which to buy anything -- including watches.
I bought a Tissot there a few years ago and when I got back to Israel found it was cheaper here (and that includes our 18% VAT rate).