I live in Washington state, and we got an “Enhanced Drivers License” (EDL) a few years ago that lets us cross back and forth from Canada.
I Googled “EDL,” and it says I can visit Mexico, Bermuda, and the Caribbean, too.
I'm surprised Panama isn't allowed, considering the large number of American expatriates who have retired there.
If you travel back and forth more than a couple times a month you may want to consider a nexus pass. It will get you expedited passage at the border. May not be a factor in Eastern Washington, but if you are crossing at Blaine, it can save lots of time.