During the Great War, or as it became known later, the First World War, the German Government expected the German American citizens to rise up and attack from within the United States. They believed that the German half of the self identification would win out. That no such thing happened is of course historical fact.
The next war, the Government believed that the Japanese Americans were a huge threat. They were not given the chance, to demonstrate their loyalty as the German Americans were, instead they were locked up in "internment camps" or if you prefer field prisons. They were investigated to the nth degree and found to be loyal to the US. No sabotage was ever conducted by these people.
In fact, the German Americans of the First World War fought heroically against the mother nation. Despite belonging as children, and adults, to various German American organizations, reading the propaganda sheets in the mother tongue, and feeling a certain sympathy for Germany during the war.
In the Second World War, the Japanese Americans were well known as the heroic members of among other units, the 442nd. We still didn't trust them enough to actually let them fight Japan, but against Germany in Europe, they performed above and beyond any reasonable standard of duty.
When I was in the Military, we had people from Puerto Rico, and several other Central and South American countries. We had Jamaicans, and we had folks from all over. They all fought, and they all risked death to serve this nation.
The funny thing is that you and the rest don't seem to mind other "ethic" celebrations. Everyone wears green on Saint Patrick's day. Everyone embraces the Irish culture in so far as they drink beer and cheer and celebrate. But God Forbid if they celebrate Cinco de Mayo. Why that is absolutely unamerican.
Calm down. Enjoy your Freedom Fries. Tell yourself that it makes you a hell of a patriot to drink bourbon and ignore foreign whiskey. Enjoy a Bud. But calm the hell down.
I know of no group that protests flying flags of other nations.
When I bought this house, there was a flag pole in the yard. There is no flag flying on it, and has not been since I moved in. I won't fly the American Flag. I won't fly it so long as the Department of Homeland Insecurity ignores the Bill of Rights. I talk people out of joining the military now, because I tell them what they would be fighting for. A Government that steals people's property, and tramples the rights of the citizens.
I have a neighbor who flys a flag, and I don't care. There is another neighbor who flys the flag of the African Continent. I don't care about that either. One flys the Gadsden Flag with the Confederate Flag. I could care less.
If someone wants to fly the Mexican Flag, I could care less. If they take down someone else's flag to put theirs up, on property they do not own or rent, then I have an issue. That would be vandalism at the least, criminal trespass, or whatever the local ordinances call it. Otherwise, I could care less.
If its your flagpole, fly what the hell you want. If it is someone else's flagpole, leave it the hell alone.