No I wouldn't make one with the USA flag, because USA isn't a culture. It's a state. A State baked in colonialism and slavery. The USA flag didn't exist before the state needed one. The design of the flag itself is based on the political reality. If I were to design anarchist iconography for north america I would use the first peoples' flags as a template, or mangle the stars and stripes so much that it becomes unrecognisable.
The baltic flags aren't like that. (Or at least the estonian one can't really speak for the other two.) They are also symbols for the people. Used to identify a culture even when the state didn't exist. A flag that's designed by a bunch of university students that then became used by a country that was just finding it's identity emerging from an oppressive overlord. At it's heart these flags were used as symbols of resistance and identity to fight against a foreign regime. Why not take it one step further and use these symbols to fight against the idea of statehood itself? As a message that we decide what our symbols are and if we want to we can take yours.
The biggest difference is that these flags don't just represent a colony. They represent a unique set of people that have their own language. The fundamental element of culture and until we create visual indicators for these languages that are separate from the states the flags are the best we have.
And as you ended you're comment with a tangential question here's mine: What do I use instead? What visual shorthand can I use to denote that this concerns the baltic region? That there are people who speak Estonian, Latvian, Lithuanian here?