apart from the met office extension, none of the weather extensions are specific to the uk .. the weatherman extension just uses the bbc weather service because it's more oriented to international weather and supports much more international cities and towns compared to u.s weather services i.e. you can use weatherman for us cities normally if not better than weather.com's very limited xml info.
for yanks, there's a weatherman f version which displays temprature in fahrenheit instead of celsius.. if your windowsversion is 2000 and above, download weatherman f NT version.
install the extension and restart kmeleon -in case of using loader.exe, you will need to terminate the loader.exe first for changes to take effect..which was probably the reason why your camouflage background did not appear in the toolbar, there's also a restart super extension which adds a menu entry to restart kmeleon with the loader so you needn't worry about closing and reopening the loader.. restart super can be downloaded from kmext under enhancements,
to setup your city, right click on the weather icon that will appear on your mainbar.. select find city code from the menu
a prompt will open to enter your city name..if you're not sure your city is supported.. just enter country name..in your case 'usa'
click ok and the bbc weather search page will open displaying all cities matching your query.. when your find your city..click on it to open its weather page
once the weather page for your city loads, right click again on the weather icon and select enter city code this time
a prompt will open and it will automatically detect if you are indeed on your city's bbc weather page and extract the city's code and display it in the enter city code prompt.. click ok
you will now get a prompt to restart kmeleon and if you are using the loader, it will also close and reopen the loader for you so changes take effect.
after kmeleon has been restarted..you will find the weather icon now displaying weather conditions for your city..to find more info about current conditions; hover on the icon and it will display temperature etc in a tooltip
to display a 3 day forecast, click once on the weather button
it will display your city's 3 day forecast at the bottom of your current page in kmeleon