Google has updated Android Pay with support for new U.S. banks, 16 in total as far as this new crop goes. If you're new to Android Pay and have never used it before, most of if not all of the large banks already support Android Pay and have for some time, so there is a very good chance that your bank or credit union already works with it. As for the new banks that were added today, They're all smaller institutions that are either local or regional, including First Federal Bank, Collins State Bank, People's Bank, and Washington Financial Bank, as well as quite a few others.
At this point Google's mobile payment solution works with a ton of different banks and credit unions, so if you're thinking about diving in and giving it a try, you'll be in for some searching to see if the establishment that you bank with is on the list. It's also worth considering that just because your bank may support the platform, it may not support it for all cards that are issued by that bank. Some institutions, for example, only supported certain credit or debit cards, or only supported credit cards from the beginning before rolling support out to debit cards as well. Taking this into consideration you may want to double check with your bank to ensure that support is available for the card that you use. What's more is that you may have to call your bank anyway to activate the card for use even if you were able to add it to the app, though this might depend on your bank.
If your bank isn't in the already supported list of institutions, whether from today or previous updates, not to worry, as Google is pretty consistent with adding new banks and credit unions to the list. For the most part new banks are added at least once a month, and sometimes every couple of weeks. For example, Google just added 24 new banks to the list of supported institutions back on September 24th, which was about a week and a half ago. That said, if your bank isn't supported yet it may be in the near future.