You can see whether a story on the Patriots'/Patriot's Day commemoration comes from Maine or Massachusetts by observing the apostrophe: if the text says Patriots', then it will be talking about Massachusetts; if it says Patriot's, then it will be talking about Maine.
(Wisconsin, which observes Patriots' Day--Massachusetts' punctuation--as a school observance day, defines patriots as follows: "“Patriots were colonists who wanted independence from British rule. Most hoped to find peaceful ways to settle their differences with England. When the British decided to look for Samuel Adams and John Hancock [two leaders of the revolutionary movement], who were hiding in Concord, Paul Revere and Billy Dawes rode through the night warning other Patriots in New England. The American Revolution began when the first shots were fired at Lexington on April 19, 1775. Each side said the other fired first. Patriots’ Day was established to mark the beginning of the Revolutionary War.”)
In 2014, according to CentralMaine.com, Sen. Chris Johnson, D-Somerville, introduced a bill to change the punctuation from a singular possessive to a plural possessive, because a constituent asked him to. Sen. Johnson thought "the Legislature should make the change to honor all the patriots of [the Lexington and Concord] battles and to model proper punctuation for students." The legislation wasn't successful.
A University of Maine at Augusta English professor, Lisa Botshon, thinks there's a third possibility, which is better than either of the possessives: just get rid of the apostrophe altogether. Without punctuation, it becomes a day about patriots rather than belonging to them (or one of them). This is called the plural attributive, and the Associated Press style book requires its use for Presidents Day, a federal holiday, now that several presidents instead of only one, are honored on that day.
All of which just goes to show that there's room for argument about use of American English even by native speakers in the U.S.