No, foreign policy in America is far from united. It's never been less united since the Civil War in the 1860's.
For instance, if you're half as cognizant of American foreign policy as you believe, then you're painfully aware of Trump's subservience not only to Putin, but also to Erdogan. He stabbed the Kurds in the back and allowed Erdogan to begin attacking them. Furthermore, he's allowed Russia to strengthen its military presence in Syria and to foment rebellion in Libya.
NOBODY in the Democratic party would consider that an example of proper American foreign policy, but it's what the Republican party has embraced in Trumpism.
It is a simple fact that the people of Macedonia have forgotten more history than America's ever experienced. Moreover, most Americans have no clue concerning the social, religious, and political divisions that has defined the Balkans since the fall of Constantinople to the Ottomans. Remember what Bismarck said in 1888: “One day the great European War will come out of some damned foolish thing in the Balkans.”
Truer words were never said.
That's why I make no excuses for any nation in the region, including Greece. The Greeks' hands are bloody, too. And recently so.
Full disclosure - I've got a nephew on Cyprus right now. And I hope you can see by what I wrote above that I have a deep appreciation and respect for the entire region's culture and history.
However, regardless of what Greece has or has not done, Macedonia needs Greece.
Yes, I said that. Why? A resurgent Turkey under the control of Erdogan, who wants to spread their power and influence as the Ottomans once did. Do I believe for a moment that Erdogan could ever do so? Of course not. If he tried, he'd learn the same hard lesson Austria-Hungary did a century ago, and for the same reasons. But he will nonetheless try to spread violence and unrest throughout the eastern Mediterranean in pursuit of his goal, and that's not good for anyone. To be sure, I'm glad Turkey is opposing the Russians in Libya...but elsewhere they're causing real problems, especially with their seeming transition into a Sunni Islamic regime that slowly coming to welcome Wahhabi extremism...which is something no nation in the Balkans wants to happen.
The Greeks are every bit as stubborn and hardheaded as everyone else in the region, including Serbia, Croatia, and Macedonia, and so for all their faults, Greece provides a stubborn, hardheaded buffer to Turkey's attempt to spread their influence. That's why the whole region needs a strong Greece.
This is realpolitik. It sucks for a great many people, but it preserves the peace...and keeping the peace must be the goal.
Lastly, if anything I said above is inaccurate or wrong, I would sincerely appreciate any correction from you. I honestly mean that, too. After all, you know much more about the region and history than I ever will. But please understand I tend to try to take the "big picture" view, to identify trends on the macro scale, even though doing so can be offensive to those who are more aware of what's happening among the people in the streets.